/* ** 2001 September 15 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* ** This is the implementation of the page cache subsystem or "pager". ** ** The pager is used to access a database disk file. It implements ** atomic commit and rollback through the use of a journal file that ** is separate from the database file. The pager also implements file ** locking to prevent two processes from writing the same database ** file simultaneously, or one process from reading the database while ** another is writing. */ #ifndef SQLITE_OMIT_DISKIO #include "sqliteInt.h" #include "wal.h" /******************* NOTES ON THE DESIGN OF THE PAGER ************************ ** ** This comment block describes invariants that hold when using a rollback ** journal. These invariants do not apply for journal_mode=WAL, ** journal_mode=MEMORY, or journal_mode=OFF. ** ** Within this comment block, a page is deemed to have been synced ** automatically as soon as it is written when PRAGMA synchronous=OFF. ** Otherwise, the page is not synced until the xSync method of the VFS ** is called successfully on the file containing the page. ** ** Definition: A page of the database file is said to be "overwriteable" if ** one or more of the following are true about the page: ** ** (a) The original content of the page as it was at the beginning of ** the transaction has been written into the rollback journal and ** synced. ** ** (b) The page was a freelist leaf page at the start of the transaction. ** ** (c) The page number is greater than the largest page that existed in ** the database file at the start of the transaction. ** ** (1) A page of the database file is never overwritten unless one of the ** following are true: ** ** (a) The page and all other pages on the same sector are overwriteable. ** ** (b) The atomic page write optimization is enabled, and the entire ** transaction other than the update of the transaction sequence ** number consists of a single page change. ** ** (2) The content of a page written into the rollback journal exactly matches ** both the content in the database when the rollback journal was written ** and the content in the database at the beginning of the current ** transaction. ** ** (3) Writes to the database file are an integer multiple of the page size ** in length and are aligned on a page boundary. ** ** (4) Reads from the database file are either aligned on a page boundary and ** an integer multiple of the page size in length or are taken from the ** first 100 bytes of the database file. ** ** (5) All writes to the database file are synced prior to the rollback journal ** being deleted, truncated, or zeroed. ** ** (6) If a super-journal file is used, then all writes to the database file ** are synced prior to the super-journal being deleted. ** ** Definition: Two databases (or the same database at two points it time) ** are said to be "logically equivalent" if they give the same answer to ** all queries. Note in particular the content of freelist leaf ** pages can be changed arbitrarily without affecting the logical equivalence ** of the database. ** ** (7) At any time, if any subset, including the empty set and the total set, ** of the unsynced changes to a rollback journal are removed and the ** journal is rolled back, the resulting database file will be logically ** equivalent to the database file at the beginning of the transaction. ** ** (8) When a transaction is rolled back, the xTruncate method of the VFS ** is called to restore the database file to the same size it was at ** the beginning of the transaction. (In some VFSes, the xTruncate ** method is a no-op, but that does not change the fact the SQLite will ** invoke it.) ** ** (9) Whenever the database file is modified, at least one bit in the range ** of bytes from 24 through 39 inclusive will be changed prior to releasing ** the EXCLUSIVE lock, thus signaling other connections on the same ** database to flush their caches. ** ** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less ** than one billion transactions. ** ** (11) A database file is well-formed at the beginning and at the conclusion ** of every transaction. ** ** (12) An EXCLUSIVE lock is held on the database file when writing to ** the database file. ** ** (13) A SHARED lock is held on the database file while reading any ** content out of the database file. ** ******************************************************************************/ /* ** Macros for troubleshooting. Normally turned off */ #if 0 int sqlite3PagerTrace=1; /* True to enable tracing */ #define sqlite3DebugPrintf printf #define PAGERTRACE(X) if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; } #else #define PAGERTRACE(X) #endif /* ** The following two macros are used within the PAGERTRACE() macros above ** to print out file-descriptors. ** ** PAGERID() takes a pointer to a Pager struct as its argument. The ** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file ** struct as its argument. */ #define PAGERID(p) (SQLITE_PTR_TO_INT(p->fd)) #define FILEHANDLEID(fd) (SQLITE_PTR_TO_INT(fd)) /* ** The Pager.eState variable stores the current 'state' of a pager. A ** pager may be in any one of the seven states shown in the following ** state diagram. ** ** OPEN <------+------+ ** | | | ** V | | ** +---------> READER-------+ | ** | | | ** | V | ** |<-------WRITER_LOCKED------> ERROR ** | | ^ ** | V | ** |<------WRITER_CACHEMOD-------->| ** | | | ** | V | ** |<-------WRITER_DBMOD---------->| ** | | | ** | V | ** +<------WRITER_FINISHED-------->+ ** ** ** List of state transitions and the C [function] that performs each: ** ** OPEN -> READER [sqlite3PagerSharedLock] ** READER -> OPEN [pager_unlock] ** ** READER -> WRITER_LOCKED [sqlite3PagerBegin] ** WRITER_LOCKED -> WRITER_CACHEMOD [pager_open_journal] ** WRITER_CACHEMOD -> WRITER_DBMOD [syncJournal] ** WRITER_DBMOD -> WRITER_FINISHED [sqlite3PagerCommitPhaseOne] ** WRITER_*** -> READER [pager_end_transaction] ** ** WRITER_*** -> ERROR [pager_error] ** ERROR -> OPEN [pager_unlock] ** ** ** OPEN: ** ** The pager starts up in this state. Nothing is guaranteed in this ** state - the file may or may not be locked and the database size is ** unknown. The database may not be read or written. ** ** * No read or write transaction is active. ** * Any lock, or no lock at all, may be held on the database file. ** * The dbSize, dbOrigSize and dbFileSize variables may not be trusted. ** ** READER: ** ** In this state all the requirements for reading the database in ** rollback (non-WAL) mode are met. Unless the pager is (or recently ** was) in exclusive-locking mode, a user-level read transaction is ** open. The database size is known in this state. ** ** A connection running with locking_mode=normal enters this state when ** it opens a read-transaction on the database and returns to state ** OPEN after the read-transaction is completed. However a connection ** running in locking_mode=exclusive (including temp databases) remains in ** this state even after the read-transaction is closed. The only way ** a locking_mode=exclusive connection can transition from READER to OPEN ** is via the ERROR state (see below). ** ** * A read transaction may be active (but a write-transaction cannot). ** * A SHARED or greater lock is held on the database file. ** * The dbSize variable may be trusted (even if a user-level read ** transaction is not active). The dbOrigSize and dbFileSize variables ** may not be trusted at this point. ** * If the database is a WAL database, then the WAL connection is open. ** * Even if a read-transaction is not open, it is guaranteed that ** there is no hot-journal in the file-system. ** ** WRITER_LOCKED: ** ** The pager moves to this state from READER when a write-transaction ** is first opened on the database. In WRITER_LOCKED state, all locks ** required to start a write-transaction are held, but no actual ** modifications to the cache or database have taken place. ** ** In rollback mode, a RESERVED or (if the transaction was opened with ** BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when ** moving to this state, but the journal file is not written to or opened ** to in this state. If the transaction is committed or rolled back while ** in WRITER_LOCKED state, all that is required is to unlock the database ** file. ** ** IN WAL mode, WalBeginWriteTransaction() is called to lock the log file. ** If the connection is running with locking_mode=exclusive, an attempt ** is made to obtain an EXCLUSIVE lock on the database file. ** ** * A write transaction is active. ** * If the connection is open in rollback-mode, a RESERVED or greater ** lock is held on the database file. ** * If the connection is open in WAL-mode, a WAL write transaction ** is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully ** called). ** * The dbSize, dbOrigSize and dbFileSize variables are all valid. ** * The contents of the pager cache have not been modified. ** * The journal file may or may not be open. ** * Nothing (not even the first header) has been written to the journal. ** ** WRITER_CACHEMOD: ** ** A pager moves from WRITER_LOCKED state to this state when a page is ** first modified by the upper layer. In rollback mode the journal file ** is opened (if it is not already open) and a header written to the ** start of it. The database file on disk has not been modified. ** ** * A write transaction is active. ** * A RESERVED or greater lock is held on the database file. ** * The journal file is open and the first header has been written ** to it, but the header has not been synced to disk. ** * The contents of the page cache have been modified. ** ** WRITER_DBMOD: ** ** The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state ** when it modifies the contents of the database file. WAL connections ** never enter this state (since they do not modify the database file, ** just the log file). ** ** * A write transaction is active. ** * An EXCLUSIVE or greater lock is held on the database file. ** * The journal file is open and the first header has been written ** and synced to disk. ** * The contents of the page cache have been modified (and possibly ** written to disk). ** ** WRITER_FINISHED: ** ** It is not possible for a WAL connection to enter this state. ** ** A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD ** state after the entire transaction has been successfully written into the ** database file. In this state the transaction may be committed simply ** by finalizing the journal file. Once in WRITER_FINISHED state, it is ** not possible to modify the database further. At this point, the upper ** layer must either commit or rollback the transaction. ** ** * A write transaction is active. ** * An EXCLUSIVE or greater lock is held on the database file. ** * All writing and syncing of journal and database data has finished. ** If no error occurred, all that remains is to finalize the journal to ** commit the transaction. If an error did occur, the caller will need ** to rollback the transaction. ** ** ERROR: ** ** The ERROR state is entered when an IO or disk-full error (including ** SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it ** difficult to be sure that the in-memory pager state (cache contents, ** db size etc.) are consistent with the contents of the file-system. ** ** Temporary pager files may enter the ERROR state, but in-memory pagers ** cannot. ** ** For example, if an IO error occurs while performing a rollback, ** the contents of the page-cache may be left in an inconsistent state. ** At this point it would be dangerous to change back to READER state ** (as usually happens after a rollback). Any subsequent readers might ** report database corruption (due to the inconsistent cache), and if ** they upgrade to writers, they may inadvertently corrupt the database ** file. To avoid this hazard, the pager switches into the ERROR state ** instead of READER following such an error. ** ** Once it has entered the ERROR state, any attempt to use the pager ** to read or write data returns an error. Eventually, once all ** outstanding transactions have been abandoned, the pager is able to ** transition back to OPEN state, discarding the contents of the ** page-cache and any other in-memory state at the same time. Everything ** is reloaded from disk (and, if necessary, hot-journal rollback peformed) ** when a read-transaction is next opened on the pager (transitioning ** the pager into READER state). At that point the system has recovered ** from the error. ** ** Specifically, the pager jumps into the ERROR state if: ** ** 1. An error occurs while attempting a rollback. This happens in ** function sqlite3PagerRollback(). ** ** 2. An error occurs while attempting to finalize a journal file ** following a commit in function sqlite3PagerCommitPhaseTwo(). ** ** 3. An error occurs while attempting to write to the journal or ** database file in function pagerStress() in order to free up ** memory. ** ** In other cases, the error is returned to the b-tree layer. The b-tree ** layer then attempts a rollback operation. If the error condition ** persists, the pager enters the ERROR state via condition (1) above. ** ** Condition (3) is necessary because it can be triggered by a read-only ** statement executed within a transaction. In this case, if the error ** code were simply returned to the user, the b-tree layer would not ** automatically attempt a rollback, as it assumes that an error in a ** read-only statement cannot leave the pager in an internally inconsistent ** state. ** ** * The Pager.errCode variable is set to something other than SQLITE_OK. ** * There are one or more outstanding references to pages (after the ** last reference is dropped the pager should move back to OPEN state). ** * The pager is not an in-memory pager. ** ** ** Notes: ** ** * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the ** connection is open in WAL mode. A WAL connection is always in one ** of the first four states. ** ** * Normally, a connection open in exclusive mode is never in PAGER_OPEN ** state. There are two exceptions: immediately after exclusive-mode has ** been turned on (and before any read or write transactions are ** executed), and when the pager is leaving the "error state". ** ** * See also: assert_pager_state(). */ #define PAGER_OPEN 0 #define PAGER_READER 1 #define PAGER_WRITER_LOCKED 2 #define PAGER_WRITER_CACHEMOD 3 #define PAGER_WRITER_DBMOD 4 #define PAGER_WRITER_FINISHED 5 #define PAGER_ERROR 6 /* ** The Pager.eLock variable is almost always set to one of the ** following locking-states, according to the lock currently held on ** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK. ** This variable is kept up to date as locks are taken and released by ** the pagerLockDb() and pagerUnlockDb() wrappers. ** ** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY ** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not ** the operation was successful. In these circumstances pagerLockDb() and ** pagerUnlockDb() take a conservative approach - eLock is always updated ** when unlocking the file, and only updated when locking the file if the ** VFS call is successful. This way, the Pager.eLock variable may be set ** to a less exclusive (lower) value than the lock that is actually held ** at the system level, but it is never set to a more exclusive value. ** ** This is usually safe. If an xUnlock fails or appears to fail, there may ** be a few redundant xLock() calls or a lock may be held for longer than ** required, but nothing really goes wrong. ** ** The exception is when the database file is unlocked as the pager moves ** from ERROR to OPEN state. At this point there may be a hot-journal file ** in the file-system that needs to be rolled back (as part of an OPEN->SHARED ** transition, by the same pager or any other). If the call to xUnlock() ** fails at this point and the pager is left holding an EXCLUSIVE lock, this ** can confuse the call to xCheckReservedLock() call made later as part ** of hot-journal detection. ** ** xCheckReservedLock() is defined as returning true "if there is a RESERVED ** lock held by this process or any others". So xCheckReservedLock may ** return true because the caller itself is holding an EXCLUSIVE lock (but ** doesn't know it because of a previous error in xUnlock). If this happens ** a hot-journal may be mistaken for a journal being created by an active ** transaction in another process, causing SQLite to read from the database ** without rolling it back. ** ** To work around this, if a call to xUnlock() fails when unlocking the ** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It ** is only changed back to a real locking state after a successful call ** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition ** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK ** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE ** lock on the database file before attempting to roll it back. See function ** PagerSharedLock() for more detail. ** ** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in ** PAGER_OPEN state. */ #define UNKNOWN_LOCK (EXCLUSIVE_LOCK+1) /* ** The maximum allowed sector size. 64KiB. If the xSectorsize() method ** returns a value larger than this, then MAX_SECTOR_SIZE is used instead. ** This could conceivably cause corruption following a power failure on ** such a system. This is currently an undocumented limit. */ #define MAX_SECTOR_SIZE 0x10000 /* ** An instance of the following structure is allocated for each active ** savepoint and statement transaction in the system. All such structures ** are stored in the Pager.aSavepoint[] array, which is allocated and ** resized using sqlite3Realloc(). ** ** When a savepoint is created, the PagerSavepoint.iHdrOffset field is ** set to 0. If a journal-header is written into the main journal while ** the savepoint is active, then iHdrOffset is set to the byte offset ** immediately following the last journal record written into the main ** journal before the journal-header. This is required during savepoint ** rollback (see pagerPlaybackSavepoint()). */ typedef struct PagerSavepoint PagerSavepoint; struct PagerSavepoint { i64 iOffset; /* Starting offset in main journal */ i64 iHdrOffset; /* See above */ Bitvec *pInSavepoint; /* Set of pages in this savepoint */ Pgno nOrig; /* Original number of pages in file */ Pgno iSubRec; /* Index of first record in sub-journal */ int bTruncateOnRelease; /* If stmt journal may be truncated on RELEASE */ #ifndef SQLITE_OMIT_WAL u32 aWalData[WAL_SAVEPOINT_NDATA]; /* WAL savepoint context */ #endif }; /* ** Bits of the Pager.doNotSpill flag. See further description below. */ #define SPILLFLAG_OFF 0x01 /* Never spill cache. Set via pragma */ #define SPILLFLAG_ROLLBACK 0x02 /* Current rolling back, so do not spill */ #define SPILLFLAG_NOSYNC 0x04 /* Spill is ok, but do not sync */ /* ** An open page cache is an instance of struct Pager. A description of ** some of the more important member variables follows: ** ** eState ** ** The current 'state' of the pager object. See the comment and state ** diagram above for a description of the pager state. ** ** eLock ** ** For a real on-disk database, the current lock held on the database file - ** NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK. ** ** For a temporary or in-memory database (neither of which require any ** locks), this variable is always set to EXCLUSIVE_LOCK. Since such ** databases always have Pager.exclusiveMode==1, this tricks the pager ** logic into thinking that it already has all the locks it will ever ** need (and no reason to release them). ** ** In some (obscure) circumstances, this variable may also be set to ** UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for ** details. ** ** changeCountDone ** ** This boolean variable is used to make sure that the change-counter ** (the 4-byte header field at byte offset 24 of the database file) is ** not updated more often than necessary. ** ** It is set to true when the change-counter field is updated, which ** can only happen if an exclusive lock is held on the database file. ** It is cleared (set to false) whenever an exclusive lock is ** relinquished on the database file. Each time a transaction is committed, ** The changeCountDone flag is inspected. If it is true, the work of ** updating the change-counter is omitted for the current transaction. ** ** This mechanism means that when running in exclusive mode, a connection ** need only update the change-counter once, for the first transaction ** committed. ** ** setSuper ** ** When PagerCommitPhaseOne() is called to commit a transaction, it may ** (or may not) specify a super-journal name to be written into the ** journal file before it is synced to disk. ** ** Whether or not a journal file contains a super-journal pointer affects ** the way in which the journal file is finalized after the transaction is ** committed or rolled back when running in "journal_mode=PERSIST" mode. ** If a journal file does not contain a super-journal pointer, it is ** finalized by overwriting the first journal header with zeroes. If ** it does contain a super-journal pointer the journal file is finalized ** by truncating it to zero bytes, just as if the connection were ** running in "journal_mode=truncate" mode. ** ** Journal files that contain super-journal pointers cannot be finalized ** simply by overwriting the first journal-header with zeroes, as the ** super-journal pointer could interfere with hot-journal rollback of any ** subsequently interrupted transaction that reuses the journal file. ** ** The flag is cleared as soon as the journal file is finalized (either ** by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the ** journal file from being successfully finalized, the setSuper flag ** is cleared anyway (and the pager will move to ERROR state). ** ** doNotSpill ** ** This variables control the behavior of cache-spills (calls made by ** the pcache module to the pagerStress() routine to write cached data ** to the file-system in order to free up memory). ** ** When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set, ** writing to the database from pagerStress() is disabled altogether. ** The SPILLFLAG_ROLLBACK case is done in a very obscure case that ** comes up during savepoint rollback that requires the pcache module ** to allocate a new page to prevent the journal file from being written ** while it is being traversed by code in pager_playback(). The SPILLFLAG_OFF ** case is a user preference. ** ** If the SPILLFLAG_NOSYNC bit is set, writing to the database from ** pagerStress() is permitted, but syncing the journal file is not. ** This flag is set by sqlite3PagerWrite() when the file-system sector-size ** is larger than the database page-size in order to prevent a journal sync ** from happening in between the journalling of two pages on the same sector. ** ** subjInMemory ** ** This is a boolean variable. If true, then any required sub-journal ** is opened as an in-memory journal file. If false, then in-memory ** sub-journals are only used for in-memory pager files. ** ** This variable is updated by the upper layer each time a new ** write-transaction is opened. ** ** dbSize, dbOrigSize, dbFileSize ** ** Variable dbSize is set to the number of pages in the database file. ** It is valid in PAGER_READER and higher states (all states except for ** OPEN and ERROR). ** ** dbSize is set based on the size of the database file, which may be ** larger than the size of the database (the value stored at offset ** 28 of the database header by the btree). If the size of the file ** is not an integer multiple of the page-size, the value stored in ** dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2). ** Except, any file that is greater than 0 bytes in size is considered ** to have at least one page. (i.e. a 1KB file with 2K page-size leads ** to dbSize==1). ** ** During a write-transaction, if pages with page-numbers greater than ** dbSize are modified in the cache, dbSize is updated accordingly. ** Similarly, if the database is truncated using PagerTruncateImage(), ** dbSize is updated. ** ** Variables dbOrigSize and dbFileSize are valid in states ** PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize ** variable at the start of the transaction. It is used during rollback, ** and to determine whether or not pages need to be journalled before ** being modified. ** ** Throughout a write-transaction, dbFileSize contains the size of ** the file on disk in pages. It is set to a copy of dbSize when the ** write-transaction is first opened, and updated when VFS calls are made ** to write or truncate the database file on disk. ** ** The only reason the dbFileSize variable is required is to suppress ** unnecessary calls to xTruncate() after committing a transaction. If, ** when a transaction is committed, the dbFileSize variable indicates ** that the database file is larger than the database image (Pager.dbSize), ** pager_truncate() is called. The pager_truncate() call uses xFilesize() ** to measure the database file on disk, and then truncates it if required. ** dbFileSize is not used when rolling back a transaction. In this case ** pager_truncate() is called unconditionally (which means there may be ** a call to xFilesize() that is not strictly required). In either case, ** pager_truncate() may cause the file to become smaller or larger. ** ** dbHintSize ** ** The dbHintSize variable is used to limit the number of calls made to ** the VFS xFileControl(FCNTL_SIZE_HINT) method. ** ** dbHintSize is set to a copy of the dbSize variable when a ** write-transaction is opened (at the same time as dbFileSize and ** dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called, ** dbHintSize is increased to the number of pages that correspond to the ** size-hint passed to the method call. See pager_write_pagelist() for ** details. ** ** errCode ** ** The Pager.errCode variable is only ever used in PAGER_ERROR state. It ** is set to zero in all other states. In PAGER_ERROR state, Pager.errCode ** is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX ** sub-codes. ** ** syncFlags, walSyncFlags ** ** syncFlags is either SQLITE_SYNC_NORMAL (0x02) or SQLITE_SYNC_FULL (0x03). ** syncFlags is used for rollback mode. walSyncFlags is used for WAL mode ** and contains the flags used to sync the checkpoint operations in the ** lower two bits, and sync flags used for transaction commits in the WAL ** file in bits 0x04 and 0x08. In other words, to get the correct sync flags ** for checkpoint operations, use (walSyncFlags&0x03) and to get the correct ** sync flags for transaction commit, use ((walSyncFlags>>2)&0x03). Note ** that with synchronous=NORMAL in WAL mode, transaction commit is not synced ** meaning that the 0x04 and 0x08 bits are both zero. */ struct Pager { sqlite3_vfs *pVfs; /* OS functions to use for IO */ u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */ u8 journalMode; /* One of the PAGER_JOURNALMODE_* values */ u8 useJournal; /* Use a rollback journal on this file */ u8 noSync; /* Do not sync the journal if true */ u8 fullSync; /* Do extra syncs of the journal for robustness */ u8 extraSync; /* sync directory after journal delete */ u8 syncFlags; /* SYNC_NORMAL or SYNC_FULL otherwise */ u8 walSyncFlags; /* See description above */ u8 tempFile; /* zFilename is a temporary or immutable file */ u8 noLock; /* Do not lock (except in WAL mode) */ u8 readOnly; /* True for a read-only database */ u8 memDb; /* True to inhibit all file I/O */ u8 memVfs; /* VFS-implemented memory database */ /************************************************************************** ** The following block contains those class members that change during ** routine operation. Class members not in this block are either fixed ** when the pager is first created or else only change when there is a ** significant mode change (such as changing the page_size, locking_mode, ** or the journal_mode). From another view, these class members describe ** the "state" of the pager, while other class members describe the ** "configuration" of the pager. */ u8 eState; /* Pager state (OPEN, READER, WRITER_LOCKED..) */ u8 eLock; /* Current lock held on database file */ u8 changeCountDone; /* Set after incrementing the change-counter */ u8 setSuper; /* Super-jrnl name is written into jrnl */ u8 doNotSpill; /* Do not spill the cache when non-zero */ u8 subjInMemory; /* True to use in-memory sub-journals */ u8 bUseFetch; /* True to use xFetch() */ u8 hasHeldSharedLock; /* True if a shared lock has ever been held */ Pgno dbSize; /* Number of pages in the database */ Pgno dbOrigSize; /* dbSize before the current transaction */ Pgno dbFileSize; /* Number of pages in the database file */ Pgno dbHintSize; /* Value passed to FCNTL_SIZE_HINT call */ int errCode; /* One of several kinds of errors */ int nRec; /* Pages journalled since last j-header written */ u32 cksumInit; /* Quasi-random value added to every checksum */ u32 nSubRec; /* Number of records written to sub-journal */ Bitvec *pInJournal; /* One bit for each page in the database file */ sqlite3_file *fd; /* File descriptor for database */ sqlite3_file *jfd; /* File descriptor for main journal */ sqlite3_file *sjfd; /* File descriptor for sub-journal */ i64 journalOff; /* Current write offset in the journal file */ i64 journalHdr; /* Byte offset to previous journal header */ sqlite3_backup *pBackup; /* Pointer to list of ongoing backup processes */ PagerSavepoint *aSavepoint; /* Array of active savepoints */ int nSavepoint; /* Number of elements in aSavepoint[] */ u32 iDataVersion; /* Changes whenever database content changes */ char dbFileVers[16]; /* Changes whenever database file changes */ int nMmapOut; /* Number of mmap pages currently outstanding */ sqlite3_int64 szMmap; /* Desired maximum mmap size */ PgHdr *pMmapFreelist; /* List of free mmap page headers (pDirty) */ /* ** End of the routinely-changing class members ***************************************************************************/ u16 nExtra; /* Add this many bytes to each in-memory page */ i16 nReserve; /* Number of unused bytes at end of each page */ u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */ u32 sectorSize; /* Assumed sector size during rollback */ Pgno mxPgno; /* Maximum allowed size of the database */ i64 pageSize; /* Number of bytes in a page */ i64 journalSizeLimit; /* Size limit for persistent journal files */ char *zFilename; /* Name of the database file */ char *zJournal; /* Name of the journal file */ int (*xBusyHandler)(void*); /* Function to call when busy */ void *pBusyHandlerArg; /* Context argument for xBusyHandler */ int aStat[4]; /* Total cache hits, misses, writes, spills */ #ifdef SQLITE_TEST int nRead; /* Database pages read */ #endif void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */ int (*xGet)(Pager*,Pgno,DbPage**,int); /* Routine to fetch a patch */ char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */ PCache *pPCache; /* Pointer to page cache object */ #ifndef SQLITE_OMIT_WAL Wal *pWal; /* Write-ahead log used by "journal_mode=wal" */ char *zWal; /* File name for write-ahead log */ #endif }; /* ** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains ** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS ** or CACHE_WRITE to sqlite3_db_status(). */ #define PAGER_STAT_HIT 0 #define PAGER_STAT_MISS 1 #define PAGER_STAT_WRITE 2 #define PAGER_STAT_SPILL 3 /* ** The following global variables hold counters used for ** testing purposes only. These variables do not exist in ** a non-testing build. These variables are not thread-safe. */ #ifdef SQLITE_TEST int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */ int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */ int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */ # define PAGER_INCR(v) v++ #else # define PAGER_INCR(v) #endif /* ** Journal files begin with the following magic string. The data ** was obtained from /dev/random. It is used only as a sanity check. ** ** Since version 2.8.0, the journal format contains additional sanity ** checking information. If the power fails while the journal is being ** written, semi-random garbage data might appear in the journal ** file after power is restored. If an attempt is then made ** to roll the journal back, the database could be corrupted. The additional ** sanity checking data is an attempt to discover the garbage in the ** journal and ignore it. ** ** The sanity checking information for the new journal format consists ** of a 32-bit checksum on each page of data. The checksum covers both ** the page number and the pPager->pageSize bytes of data for the page. ** This cksum is initialized to a 32-bit random value that appears in the ** journal file right after the header. The random initializer is important, ** because garbage data that appears at the end of a journal is likely ** data that was once in other files that have now been deleted. If the ** garbage data came from an obsolete journal file, the checksums might ** be correct. But by initializing the checksum to random value which ** is different for every journal, we minimize that risk. */ static const unsigned char aJournalMagic[] = { 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7, }; /* ** The size of the of each page record in the journal is given by ** the following macro. */ #define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8) /* ** The journal header size for this pager. This is usually the same ** size as a single disk sector. See also setSectorSize(). */ #define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize) /* ** The macro MEMDB is true if we are dealing with an in-memory database. ** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set, ** the value of MEMDB will be a constant and the compiler will optimize ** out code that would never execute. */ #ifdef SQLITE_OMIT_MEMORYDB # define MEMDB 0 #else # define MEMDB pPager->memDb #endif /* ** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch ** interfaces to access the database using memory-mapped I/O. */ #if SQLITE_MAX_MMAP_SIZE>0 # define USEFETCH(x) ((x)->bUseFetch) #else # define USEFETCH(x) 0 #endif /* ** The argument to this macro is a file descriptor (type sqlite3_file*). ** Return 0 if it is not open, or non-zero (but not 1) if it is. ** ** This is so that expressions can be written as: ** ** if( isOpen(pPager->jfd) ){ ... ** ** instead of ** ** if( pPager->jfd->pMethods ){ ... */ #define isOpen(pFd) ((pFd)->pMethods!=0) #ifdef SQLITE_DIRECT_OVERFLOW_READ /* ** Return true if page pgno can be read directly from the database file ** by the b-tree layer. This is the case if: ** ** * the database file is open, ** * there are no dirty pages in the cache, and ** * the desired page is not currently in the wal file. */ int sqlite3PagerDirectReadOk(Pager *pPager, Pgno pgno){ if( pPager->fd->pMethods==0 ) return 0; if( sqlite3PCacheIsDirty(pPager->pPCache) ) return 0; #ifndef SQLITE_OMIT_WAL if( pPager->pWal ){ u32 iRead = 0; int rc; rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iRead); return (rc==SQLITE_OK && iRead==0); } #endif return 1; } #endif #ifndef SQLITE_OMIT_WAL # define pagerUseWal(x) ((x)->pWal!=0) #else # define pagerUseWal(x) 0 # define pagerRollbackWal(x) 0 # define pagerWalFrames(v,w,x,y) 0 # define pagerOpenWalIfPresent(z) SQLITE_OK # define pagerBeginReadTransaction(z) SQLITE_OK #endif #ifndef NDEBUG /* ** Usage: ** ** assert( assert_pager_state(pPager) ); ** ** This function runs many asserts to try to find inconsistencies in ** the internal state of the Pager object. */ static int assert_pager_state(Pager *p){ Pager *pPager = p; /* State must be valid. */ assert( p->eState==PAGER_OPEN || p->eState==PAGER_READER || p->eState==PAGER_WRITER_LOCKED || p->eState==PAGER_WRITER_CACHEMOD || p->eState==PAGER_WRITER_DBMOD || p->eState==PAGER_WRITER_FINISHED || p->eState==PAGER_ERROR ); /* Regardless of the current state, a temp-file connection always behaves ** as if it has an exclusive lock on the database file. It never updates ** the change-counter field, so the changeCountDone flag is always set. */ assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK ); assert( p->tempFile==0 || pPager->changeCountDone ); /* If the useJournal flag is clear, the journal-mode must be "OFF". ** And if the journal-mode is "OFF", the journal file must not be open. */ assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal ); assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) ); /* Check that MEMDB implies noSync. And an in-memory journal. Since ** this means an in-memory pager performs no IO at all, it cannot encounter ** either SQLITE_IOERR or SQLITE_FULL during rollback or while finalizing ** a journal file. (although the in-memory journal implementation may ** return SQLITE_IOERR_NOMEM while the journal file is being written). It ** is therefore not possible for an in-memory pager to enter the ERROR ** state. */ if( MEMDB ){ assert( !isOpen(p->fd) ); assert( p->noSync ); assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->journalMode==PAGER_JOURNALMODE_MEMORY ); assert( p->eState!=PAGER_ERROR && p->eState!=PAGER_OPEN ); assert( pagerUseWal(p)==0 ); } /* If changeCountDone is set, a RESERVED lock or greater must be held ** on the file. */ assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK ); assert( p->eLock!=PENDING_LOCK ); switch( p->eState ){ case PAGER_OPEN: assert( !MEMDB ); assert( pPager->errCode==SQLITE_OK ); assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile ); break; case PAGER_READER: assert( pPager->errCode==SQLITE_OK ); assert( p->eLock!=UNKNOWN_LOCK ); assert( p->eLock>=SHARED_LOCK ); break; case PAGER_WRITER_LOCKED: assert( p->eLock!=UNKNOWN_LOCK ); assert( pPager->errCode==SQLITE_OK ); if( !pagerUseWal(pPager) ){ assert( p->eLock>=RESERVED_LOCK ); } assert( pPager->dbSize==pPager->dbOrigSize ); assert( pPager->dbOrigSize==pPager->dbFileSize ); assert( pPager->dbOrigSize==pPager->dbHintSize ); assert( pPager->setSuper==0 ); break; case PAGER_WRITER_CACHEMOD: assert( p->eLock!=UNKNOWN_LOCK ); assert( pPager->errCode==SQLITE_OK ); if( !pagerUseWal(pPager) ){ /* It is possible that if journal_mode=wal here that neither the ** journal file nor the WAL file are open. This happens during ** a rollback transaction that switches from journal_mode=off ** to journal_mode=wal. */ assert( p->eLock>=RESERVED_LOCK ); assert( isOpen(p->jfd) || p->journalMode==PAGER_JOURNALMODE_OFF || p->journalMode==PAGER_JOURNALMODE_WAL ); } assert( pPager->dbOrigSize==pPager->dbFileSize ); assert( pPager->dbOrigSize==pPager->dbHintSize ); break; case PAGER_WRITER_DBMOD: assert( p->eLock==EXCLUSIVE_LOCK ); assert( pPager->errCode==SQLITE_OK ); assert( !pagerUseWal(pPager) ); assert( p->eLock>=EXCLUSIVE_LOCK ); assert( isOpen(p->jfd) || p->journalMode==PAGER_JOURNALMODE_OFF || p->journalMode==PAGER_JOURNALMODE_WAL || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC) ); assert( pPager->dbOrigSize<=pPager->dbHintSize ); break; case PAGER_WRITER_FINISHED: assert( p->eLock==EXCLUSIVE_LOCK ); assert( pPager->errCode==SQLITE_OK ); assert( !pagerUseWal(pPager) ); assert( isOpen(p->jfd) || p->journalMode==PAGER_JOURNALMODE_OFF || p->journalMode==PAGER_JOURNALMODE_WAL || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC) ); break; case PAGER_ERROR: /* There must be at least one outstanding reference to the pager if ** in ERROR state. Otherwise the pager should have already dropped ** back to OPEN state. */ assert( pPager->errCode!=SQLITE_OK ); assert( sqlite3PcacheRefCount(pPager->pPCache)>0 || pPager->tempFile ); break; } return 1; } #endif /* ifndef NDEBUG */ #ifdef SQLITE_DEBUG /* ** Return a pointer to a human readable string in a static buffer ** containing the state of the Pager object passed as an argument. This ** is intended to be used within debuggers. For example, as an alternative ** to "print *pPager" in gdb: ** ** (gdb) printf "%s", print_pager_state(pPager) ** ** This routine has external linkage in order to suppress compiler warnings ** about an unused function. It is enclosed within SQLITE_DEBUG and so does ** not appear in normal builds. */ char *print_pager_state(Pager *p){ static char zRet[1024]; sqlite3_snprintf(1024, zRet, "Filename: %s\n" "State: %s errCode=%d\n" "Lock: %s\n" "Locking mode: locking_mode=%s\n" "Journal mode: journal_mode=%s\n" "Backing store: tempFile=%d memDb=%d useJournal=%d\n" "Journal: journalOff=%lld journalHdr=%lld\n" "Size: dbsize=%d dbOrigSize=%d dbFileSize=%d\n" , p->zFilename , p->eState==PAGER_OPEN ? "OPEN" : p->eState==PAGER_READER ? "READER" : p->eState==PAGER_WRITER_LOCKED ? "WRITER_LOCKED" : p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" : p->eState==PAGER_WRITER_DBMOD ? "WRITER_DBMOD" : p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" : p->eState==PAGER_ERROR ? "ERROR" : "?error?" , (int)p->errCode , p->eLock==NO_LOCK ? "NO_LOCK" : p->eLock==RESERVED_LOCK ? "RESERVED" : p->eLock==EXCLUSIVE_LOCK ? "EXCLUSIVE" : p->eLock==SHARED_LOCK ? "SHARED" : p->eLock==UNKNOWN_LOCK ? "UNKNOWN" : "?error?" , p->exclusiveMode ? "exclusive" : "normal" , p->journalMode==PAGER_JOURNALMODE_MEMORY ? "memory" : p->journalMode==PAGER_JOURNALMODE_OFF ? "off" : p->journalMode==PAGER_JOURNALMODE_DELETE ? "delete" : p->journalMode==PAGER_JOURNALMODE_PERSIST ? "persist" : p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" : p->journalMode==PAGER_JOURNALMODE_WAL ? "wal" : "?error?" , (int)p->tempFile, (int)p->memDb, (int)p->useJournal , p->journalOff, p->journalHdr , (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize ); return zRet; } #endif /* Forward references to the various page getters */ static int getPageNormal(Pager*,Pgno,DbPage**,int); static int getPageError(Pager*,Pgno,DbPage**,int); #if SQLITE_MAX_MMAP_SIZE>0 static int getPageMMap(Pager*,Pgno,DbPage**,int); #endif /* ** Set the Pager.xGet method for the appropriate routine used to fetch ** content from the pager. */ static void setGetterMethod(Pager *pPager){ if( pPager->errCode ){ pPager->xGet = getPageError; #if SQLITE_MAX_MMAP_SIZE>0 }else if( USEFETCH(pPager) ){ pPager->xGet = getPageMMap; #endif /* SQLITE_MAX_MMAP_SIZE>0 */ }else{ pPager->xGet = getPageNormal; } } /* ** Return true if it is necessary to write page *pPg into the sub-journal. ** A page needs to be written into the sub-journal if there exists one ** or more open savepoints for which: ** ** * The page-number is less than or equal to PagerSavepoint.nOrig, and ** * The bit corresponding to the page-number is not set in ** PagerSavepoint.pInSavepoint. */ static int subjRequiresPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; PagerSavepoint *p; Pgno pgno = pPg->pgno; int i; for(i=0; inSavepoint; i++){ p = &pPager->aSavepoint[i]; if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){ for(i=i+1; inSavepoint; i++){ pPager->aSavepoint[i].bTruncateOnRelease = 0; } return 1; } } return 0; } #ifdef SQLITE_DEBUG /* ** Return true if the page is already in the journal file. */ static int pageInJournal(Pager *pPager, PgHdr *pPg){ return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno); } #endif /* ** Read a 32-bit integer from the given file descriptor. Store the integer ** that is read in *pRes. Return SQLITE_OK if everything worked, or an ** error code is something goes wrong. ** ** All values are stored on disk as big-endian. */ static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){ unsigned char ac[4]; int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset); if( rc==SQLITE_OK ){ *pRes = sqlite3Get4byte(ac); } return rc; } /* ** Write a 32-bit integer into a string buffer in big-endian byte order. */ #define put32bits(A,B) sqlite3Put4byte((u8*)A,B) /* ** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK ** on success or an error code is something goes wrong. */ static int write32bits(sqlite3_file *fd, i64 offset, u32 val){ char ac[4]; put32bits(ac, val); return sqlite3OsWrite(fd, ac, 4, offset); } /* ** Unlock the database file to level eLock, which must be either NO_LOCK ** or SHARED_LOCK. Regardless of whether or not the call to xUnlock() ** succeeds, set the Pager.eLock variable to match the (attempted) new lock. ** ** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is ** called, do not modify it. See the comment above the #define of ** UNKNOWN_LOCK for an explanation of this. */ static int pagerUnlockDb(Pager *pPager, int eLock){ int rc = SQLITE_OK; assert( !pPager->exclusiveMode || pPager->eLock==eLock ); assert( eLock==NO_LOCK || eLock==SHARED_LOCK ); assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 ); if( isOpen(pPager->fd) ){ assert( pPager->eLock>=eLock ); rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock); if( pPager->eLock!=UNKNOWN_LOCK ){ pPager->eLock = (u8)eLock; } IOTRACE(("UNLOCK %p %d\n", pPager, eLock)) } pPager->changeCountDone = pPager->tempFile; /* ticket fb3b3024ea238d5c */ return rc; } /* ** Lock the database file to level eLock, which must be either SHARED_LOCK, ** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the ** Pager.eLock variable to the new locking state. ** ** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is ** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK. ** See the comment above the #define of UNKNOWN_LOCK for an explanation ** of this. */ static int pagerLockDb(Pager *pPager, int eLock){ int rc = SQLITE_OK; assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK ); if( pPager->eLockeLock==UNKNOWN_LOCK ){ rc = pPager->noLock ? SQLITE_OK : sqlite3OsLock(pPager->fd, eLock); if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){ pPager->eLock = (u8)eLock; IOTRACE(("LOCK %p %d\n", pPager, eLock)) } } return rc; } /* ** This function determines whether or not the atomic-write or ** atomic-batch-write optimizations can be used with this pager. The ** atomic-write optimization can be used if: ** ** (a) the value returned by OsDeviceCharacteristics() indicates that ** a database page may be written atomically, and ** (b) the value returned by OsSectorSize() is less than or equal ** to the page size. ** ** If it can be used, then the value returned is the size of the journal ** file when it contains rollback data for exactly one page. ** ** The atomic-batch-write optimization can be used if OsDeviceCharacteristics() ** returns a value with the SQLITE_IOCAP_BATCH_ATOMIC bit set. -1 is ** returned in this case. ** ** If neither optimization can be used, 0 is returned. */ static int jrnlBufferSize(Pager *pPager){ assert( !MEMDB ); #if defined(SQLITE_ENABLE_ATOMIC_WRITE) \ || defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE) int dc; /* Device characteristics */ assert( isOpen(pPager->fd) ); dc = sqlite3OsDeviceCharacteristics(pPager->fd); #else UNUSED_PARAMETER(pPager); #endif #ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE if( pPager->dbSize>0 && (dc&SQLITE_IOCAP_BATCH_ATOMIC) ){ return -1; } #endif #ifdef SQLITE_ENABLE_ATOMIC_WRITE { int nSector = pPager->sectorSize; int szPage = pPager->pageSize; assert(SQLITE_IOCAP_ATOMIC512==(512>>8)); assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8)); if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){ return 0; } } return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager); #endif return 0; } /* ** If SQLITE_CHECK_PAGES is defined then we do some sanity checking ** on the cache using a hash function. This is used for testing ** and debugging only. */ #ifdef SQLITE_CHECK_PAGES /* ** Return a 32-bit hash of the page data for pPage. */ static u32 pager_datahash(int nByte, unsigned char *pData){ u32 hash = 0; int i; for(i=0; ipPager->pageSize, (unsigned char *)pPage->pData); } static void pager_set_pagehash(PgHdr *pPage){ pPage->pageHash = pager_pagehash(pPage); } /* ** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES ** is defined, and NDEBUG is not defined, an assert() statement checks ** that the page is either dirty or still matches the calculated page-hash. */ #define CHECK_PAGE(x) checkPage(x) static void checkPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; assert( pPager->eState!=PAGER_ERROR ); assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) ); } #else #define pager_datahash(X,Y) 0 #define pager_pagehash(X) 0 #define pager_set_pagehash(X) #define CHECK_PAGE(x) #endif /* SQLITE_CHECK_PAGES */ /* ** When this is called the journal file for pager pPager must be open. ** This function attempts to read a super-journal file name from the ** end of the file and, if successful, copies it into memory supplied ** by the caller. See comments above writeSuperJournal() for the format ** used to store a super-journal file name at the end of a journal file. ** ** zSuper must point to a buffer of at least nSuper bytes allocated by ** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is ** enough space to write the super-journal name). If the super-journal ** name in the journal is longer than nSuper bytes (including a ** nul-terminator), then this is handled as if no super-journal name ** were present in the journal. ** ** If a super-journal file name is present at the end of the journal ** file, then it is copied into the buffer pointed to by zSuper. A ** nul-terminator byte is appended to the buffer following the ** super-journal file name. ** ** If it is determined that no super-journal file name is present ** zSuper[0] is set to 0 and SQLITE_OK returned. ** ** If an error occurs while reading from the journal file, an SQLite ** error code is returned. */ static int readSuperJournal(sqlite3_file *pJrnl, char *zSuper, u32 nSuper){ int rc; /* Return code */ u32 len; /* Length in bytes of super-journal name */ i64 szJ; /* Total size in bytes of journal file pJrnl */ u32 cksum; /* MJ checksum value read from journal */ u32 u; /* Unsigned loop counter */ unsigned char aMagic[8]; /* A buffer to hold the magic header */ zSuper[0] = '\0'; if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ)) || szJ<16 || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len)) || len>=nSuper || len>szJ-16 || len==0 || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum)) || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8)) || memcmp(aMagic, aJournalMagic, 8) || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zSuper, len, szJ-16-len)) ){ return rc; } /* See if the checksum matches the super-journal name */ for(u=0; ujournalOff, assuming a sector ** size of pPager->sectorSize bytes. ** ** i.e for a sector size of 512: ** ** Pager.journalOff Return value ** --------------------------------------- ** 0 0 ** 512 512 ** 100 512 ** 2000 2048 ** */ static i64 journalHdrOffset(Pager *pPager){ i64 offset = 0; i64 c = pPager->journalOff; if( c ){ offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager); } assert( offset%JOURNAL_HDR_SZ(pPager)==0 ); assert( offset>=c ); assert( (offset-c)jfd) ); assert( !sqlite3JournalIsInMemory(pPager->jfd) ); if( pPager->journalOff ){ const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */ IOTRACE(("JZEROHDR %p\n", pPager)) if( doTruncate || iLimit==0 ){ rc = sqlite3OsTruncate(pPager->jfd, 0); }else{ static const char zeroHdr[28] = {0}; rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0); } if( rc==SQLITE_OK && !pPager->noSync ){ rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags); } /* At this point the transaction is committed but the write lock ** is still held on the file. If there is a size limit configured for ** the persistent journal and the journal file currently consumes more ** space than that limit allows for, truncate it now. There is no need ** to sync the file following this operation. */ if( rc==SQLITE_OK && iLimit>0 ){ i64 sz; rc = sqlite3OsFileSize(pPager->jfd, &sz); if( rc==SQLITE_OK && sz>iLimit ){ rc = sqlite3OsTruncate(pPager->jfd, iLimit); } } } return rc; } /* ** The journal file must be open when this routine is called. A journal ** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the ** current location. ** ** The format for the journal header is as follows: ** - 8 bytes: Magic identifying journal format. ** - 4 bytes: Number of records in journal, or -1 no-sync mode is on. ** - 4 bytes: Random number used for page hash. ** - 4 bytes: Initial database page count. ** - 4 bytes: Sector size used by the process that wrote this journal. ** - 4 bytes: Database page size. ** ** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space. */ static int writeJournalHdr(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */ u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */ u32 nWrite; /* Bytes of header sector written */ int ii; /* Loop counter */ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ if( nHeader>JOURNAL_HDR_SZ(pPager) ){ nHeader = JOURNAL_HDR_SZ(pPager); } /* If there are active savepoints and any of them were created ** since the most recent journal header was written, update the ** PagerSavepoint.iHdrOffset fields now. */ for(ii=0; iinSavepoint; ii++){ if( pPager->aSavepoint[ii].iHdrOffset==0 ){ pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff; } } pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager); /* ** Write the nRec Field - the number of page records that follow this ** journal header. Normally, zero is written to this value at this time. ** After the records are added to the journal (and the journal synced, ** if in full-sync mode), the zero is overwritten with the true number ** of records (see syncJournal()). ** ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When ** reading the journal this value tells SQLite to assume that the ** rest of the journal file contains valid page records. This assumption ** is dangerous, as if a failure occurred whilst writing to the journal ** file it may contain some garbage data. There are two scenarios ** where this risk can be ignored: ** ** * When the pager is in no-sync mode. Corruption can follow a ** power failure in this case anyway. ** ** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees ** that garbage data is never appended to the journal file. */ assert( isOpen(pPager->fd) || pPager->noSync ); if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY) || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND) ){ memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic)); put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff); }else{ memset(zHeader, 0, sizeof(aJournalMagic)+4); } /* The random check-hash initializer */ sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit); put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit); /* The initial database size */ put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize); /* The assumed sector size for this process */ put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize); /* The page size */ put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize); /* Initializing the tail of the buffer is not necessary. Everything ** works find if the following memset() is omitted. But initializing ** the memory prevents valgrind from complaining, so we are willing to ** take the performance hit. */ memset(&zHeader[sizeof(aJournalMagic)+20], 0, nHeader-(sizeof(aJournalMagic)+20)); /* In theory, it is only necessary to write the 28 bytes that the ** journal header consumes to the journal file here. Then increment the ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next ** record is written to the following sector (leaving a gap in the file ** that will be implicitly filled in by the OS). ** ** However it has been discovered that on some systems this pattern can ** be significantly slower than contiguously writing data to the file, ** even if that means explicitly writing data to the block of ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what ** is done. ** ** The loop is required here in case the sector-size is larger than the ** database page size. Since the zHeader buffer is only Pager.pageSize ** bytes in size, more than one call to sqlite3OsWrite() may be required ** to populate the entire journal header sector. */ for(nWrite=0; rc==SQLITE_OK&&nWritejournalHdr, nHeader)) rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff); assert( pPager->journalHdr <= pPager->journalOff ); pPager->journalOff += nHeader; } return rc; } /* ** The journal file must be open when this is called. A journal header file ** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal ** file. The current location in the journal file is given by ** pPager->journalOff. See comments above function writeJournalHdr() for ** a description of the journal header format. ** ** If the header is read successfully, *pNRec is set to the number of ** page records following this header and *pDbSize is set to the size of the ** database before the transaction began, in pages. Also, pPager->cksumInit ** is set to the value read from the journal header. SQLITE_OK is returned ** in this case. ** ** If the journal header file appears to be corrupted, SQLITE_DONE is ** returned and *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes ** cannot be read from the journal file an error code is returned. */ static int readJournalHdr( Pager *pPager, /* Pager object */ int isHot, i64 journalSize, /* Size of the open journal file in bytes */ u32 *pNRec, /* OUT: Value read from the nRec field */ u32 *pDbSize /* OUT: Value of original database size field */ ){ int rc; /* Return code */ unsigned char aMagic[8]; /* A buffer to hold the magic header */ i64 iHdrOff; /* Offset of journal header being read */ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ /* Advance Pager.journalOff to the start of the next sector. If the ** journal file is too small for there to be a header stored at this ** point, return SQLITE_DONE. */ pPager->journalOff = journalHdrOffset(pPager); if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){ return SQLITE_DONE; } iHdrOff = pPager->journalOff; /* Read in the first 8 bytes of the journal header. If they do not match ** the magic string found at the start of each journal header, return ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise, ** proceed. */ if( isHot || iHdrOff!=pPager->journalHdr ){ rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff); if( rc ){ return rc; } if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){ return SQLITE_DONE; } } /* Read the first three 32-bit fields of the journal header: The nRec ** field, the checksum-initializer and the database size at the start ** of the transaction. Return an error code if anything goes wrong. */ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize)) ){ return rc; } if( pPager->journalOff==0 ){ u32 iPageSize; /* Page-size field of journal header */ u32 iSectorSize; /* Sector-size field of journal header */ /* Read the page-size and sector-size journal header fields. */ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize)) ){ return rc; } /* Versions of SQLite prior to 3.5.8 set the page-size field of the ** journal header to zero. In this case, assume that the Pager.pageSize ** variable is already set to the correct page size. */ if( iPageSize==0 ){ iPageSize = pPager->pageSize; } /* Check that the values read from the page-size and sector-size fields ** are within range. To be 'in range', both values need to be a power ** of two greater than or equal to 512 or 32, and not greater than their ** respective compile time maximum limits. */ if( iPageSize<512 || iSectorSize<32 || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE || ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0 ){ /* If the either the page-size or sector-size in the journal-header is ** invalid, then the process that wrote the journal-header must have ** crashed before the header was synced. In this case stop reading ** the journal file here. */ return SQLITE_DONE; } /* Update the page-size to match the value read from the journal. ** Use a testcase() macro to make sure that malloc failure within ** PagerSetPagesize() is tested. */ rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1); testcase( rc!=SQLITE_OK ); /* Update the assumed sector-size to match the value used by ** the process that created this journal. If this journal was ** created by a process other than this one, then this routine ** is being called from within pager_playback(). The local value ** of Pager.sectorSize is restored at the end of that routine. */ pPager->sectorSize = iSectorSize; } pPager->journalOff += JOURNAL_HDR_SZ(pPager); return rc; } /* ** Write the supplied super-journal name into the journal file for pager ** pPager at the current location. The super-journal name must be the last ** thing written to a journal file. If the pager is in full-sync mode, the ** journal file descriptor is advanced to the next sector boundary before ** anything is written. The format is: ** ** + 4 bytes: PAGER_MJ_PGNO. ** + N bytes: super-journal filename in utf-8. ** + 4 bytes: N (length of super-journal name in bytes, no nul-terminator). ** + 4 bytes: super-journal name checksum. ** + 8 bytes: aJournalMagic[]. ** ** The super-journal page checksum is the sum of the bytes in thesuper-journal ** name, where each byte is interpreted as a signed 8-bit integer. ** ** If zSuper is a NULL pointer (occurs for a single database transaction), ** this call is a no-op. */ static int writeSuperJournal(Pager *pPager, const char *zSuper){ int rc; /* Return code */ int nSuper; /* Length of string zSuper */ i64 iHdrOff; /* Offset of header in journal file */ i64 jrnlSize; /* Size of journal file on disk */ u32 cksum = 0; /* Checksum of string zSuper */ assert( pPager->setSuper==0 ); assert( !pagerUseWal(pPager) ); if( !zSuper || pPager->journalMode==PAGER_JOURNALMODE_MEMORY || !isOpen(pPager->jfd) ){ return SQLITE_OK; } pPager->setSuper = 1; assert( pPager->journalHdr <= pPager->journalOff ); /* Calculate the length in bytes and the checksum of zSuper */ for(nSuper=0; zSuper[nSuper]; nSuper++){ cksum += zSuper[nSuper]; } /* If in full-sync mode, advance to the next disk sector before writing ** the super-journal name. This is in case the previous page written to ** the journal has already been synced. */ if( pPager->fullSync ){ pPager->journalOff = journalHdrOffset(pPager); } iHdrOff = pPager->journalOff; /* Write the super-journal data to the end of the journal file. If ** an error occurs, return the error code to the caller. */ if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager)))) || (0 != (rc = sqlite3OsWrite(pPager->jfd, zSuper, nSuper, iHdrOff+4))) || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper, nSuper))) || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper+4, cksum))) || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, iHdrOff+4+nSuper+8))) ){ return rc; } pPager->journalOff += (nSuper+20); /* If the pager is in peristent-journal mode, then the physical ** journal-file may extend past the end of the super-journal name ** and 8 bytes of magic data just written to the file. This is ** dangerous because the code to rollback a hot-journal file ** will not be able to find the super-journal name to determine ** whether or not the journal is hot. ** ** Easiest thing to do in this scenario is to truncate the journal ** file to the required size. */ if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize)) && jrnlSize>pPager->journalOff ){ rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff); } return rc; } /* ** Discard the entire contents of the in-memory page-cache. */ static void pager_reset(Pager *pPager){ pPager->iDataVersion++; sqlite3BackupRestart(pPager->pBackup); sqlite3PcacheClear(pPager->pPCache); } /* ** Return the pPager->iDataVersion value */ u32 sqlite3PagerDataVersion(Pager *pPager){ return pPager->iDataVersion; } /* ** Free all structures in the Pager.aSavepoint[] array and set both ** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal ** if it is open and the pager is not in exclusive mode. */ static void releaseAllSavepoints(Pager *pPager){ int ii; /* Iterator for looping through Pager.aSavepoint */ for(ii=0; iinSavepoint; ii++){ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); } if( !pPager->exclusiveMode || sqlite3JournalIsInMemory(pPager->sjfd) ){ sqlite3OsClose(pPager->sjfd); } sqlite3_free(pPager->aSavepoint); pPager->aSavepoint = 0; pPager->nSavepoint = 0; pPager->nSubRec = 0; } /* ** Set the bit number pgno in the PagerSavepoint.pInSavepoint ** bitvecs of all open savepoints. Return SQLITE_OK if successful ** or SQLITE_NOMEM if a malloc failure occurs. */ static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){ int ii; /* Loop counter */ int rc = SQLITE_OK; /* Result code */ for(ii=0; iinSavepoint; ii++){ PagerSavepoint *p = &pPager->aSavepoint[ii]; if( pgno<=p->nOrig ){ rc |= sqlite3BitvecSet(p->pInSavepoint, pgno); testcase( rc==SQLITE_NOMEM ); assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); } } return rc; } /* ** This function is a no-op if the pager is in exclusive mode and not ** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN ** state. ** ** If the pager is not in exclusive-access mode, the database file is ** completely unlocked. If the file is unlocked and the file-system does ** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is ** closed (if it is open). ** ** If the pager is in ERROR state when this function is called, the ** contents of the pager cache are discarded before switching back to ** the OPEN state. Regardless of whether the pager is in exclusive-mode ** or not, any journal file left in the file-system will be treated ** as a hot-journal and rolled back the next time a read-transaction ** is opened (by this or by any other connection). */ static void pager_unlock(Pager *pPager){ assert( pPager->eState==PAGER_READER || pPager->eState==PAGER_OPEN || pPager->eState==PAGER_ERROR ); sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; releaseAllSavepoints(pPager); if( pagerUseWal(pPager) ){ assert( !isOpen(pPager->jfd) ); sqlite3WalEndReadTransaction(pPager->pWal); pPager->eState = PAGER_OPEN; }else if( !pPager->exclusiveMode ){ int rc; /* Error code returned by pagerUnlockDb() */ int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0; /* If the operating system support deletion of open files, then ** close the journal file when dropping the database lock. Otherwise ** another connection with journal_mode=delete might delete the file ** out from under us. */ assert( (PAGER_JOURNALMODE_MEMORY & 5)!=1 ); assert( (PAGER_JOURNALMODE_OFF & 5)!=1 ); assert( (PAGER_JOURNALMODE_WAL & 5)!=1 ); assert( (PAGER_JOURNALMODE_DELETE & 5)!=1 ); assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 ); assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 ); if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN) || 1!=(pPager->journalMode & 5) ){ sqlite3OsClose(pPager->jfd); } /* If the pager is in the ERROR state and the call to unlock the database ** file fails, set the current lock to UNKNOWN_LOCK. See the comment ** above the #define for UNKNOWN_LOCK for an explanation of why this ** is necessary. */ rc = pagerUnlockDb(pPager, NO_LOCK); if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){ pPager->eLock = UNKNOWN_LOCK; } /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here ** without clearing the error code. This is intentional - the error ** code is cleared and the cache reset in the block below. */ assert( pPager->errCode || pPager->eState!=PAGER_ERROR ); pPager->eState = PAGER_OPEN; } /* If Pager.errCode is set, the contents of the pager cache cannot be ** trusted. Now that there are no outstanding references to the pager, ** it can safely move back to PAGER_OPEN state. This happens in both ** normal and exclusive-locking mode. */ assert( pPager->errCode==SQLITE_OK || !MEMDB ); if( pPager->errCode ){ if( pPager->tempFile==0 ){ pager_reset(pPager); pPager->changeCountDone = 0; pPager->eState = PAGER_OPEN; }else{ pPager->eState = (isOpen(pPager->jfd) ? PAGER_OPEN : PAGER_READER); } if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0); pPager->errCode = SQLITE_OK; setGetterMethod(pPager); } pPager->journalOff = 0; pPager->journalHdr = 0; pPager->setSuper = 0; } /* ** This function is called whenever an IOERR or FULL error that requires ** the pager to transition into the ERROR state may ahve occurred. ** The first argument is a pointer to the pager structure, the second ** the error-code about to be returned by a pager API function. The ** value returned is a copy of the second argument to this function. ** ** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the ** IOERR sub-codes, the pager enters the ERROR state and the error code ** is stored in Pager.errCode. While the pager remains in the ERROR state, ** all major API calls on the Pager will immediately return Pager.errCode. ** ** The ERROR state indicates that the contents of the pager-cache ** cannot be trusted. This state can be cleared by completely discarding ** the contents of the pager-cache. If a transaction was active when ** the persistent error occurred, then the rollback journal may need ** to be replayed to restore the contents of the database file (as if ** it were a hot-journal). */ static int pager_error(Pager *pPager, int rc){ int rc2 = rc & 0xff; assert( rc==SQLITE_OK || !MEMDB ); assert( pPager->errCode==SQLITE_FULL || pPager->errCode==SQLITE_OK || (pPager->errCode & 0xff)==SQLITE_IOERR ); if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){ pPager->errCode = rc; pPager->eState = PAGER_ERROR; setGetterMethod(pPager); } return rc; } static int pager_truncate(Pager *pPager, Pgno nPage); /* ** The write transaction open on pPager is being committed (bCommit==1) ** or rolled back (bCommit==0). ** ** Return TRUE if and only if all dirty pages should be flushed to disk. ** ** Rules: ** ** * For non-TEMP databases, always sync to disk. This is necessary ** for transactions to be durable. ** ** * Sync TEMP database only on a COMMIT (not a ROLLBACK) when the backing ** file has been created already (via a spill on pagerStress()) and ** when the number of dirty pages in memory exceeds 25% of the total ** cache size. */ static int pagerFlushOnCommit(Pager *pPager, int bCommit){ if( pPager->tempFile==0 ) return 1; if( !bCommit ) return 0; if( !isOpen(pPager->fd) ) return 0; return (sqlite3PCachePercentDirty(pPager->pPCache)>=25); } /* ** This routine ends a transaction. A transaction is usually ended by ** either a COMMIT or a ROLLBACK operation. This routine may be called ** after rollback of a hot-journal, or if an error occurs while opening ** the journal file or writing the very first journal-header of a ** database transaction. ** ** This routine is never called in PAGER_ERROR state. If it is called ** in PAGER_NONE or PAGER_SHARED state and the lock held is less ** exclusive than a RESERVED lock, it is a no-op. ** ** Otherwise, any active savepoints are released. ** ** If the journal file is open, then it is "finalized". Once a journal ** file has been finalized it is not possible to use it to roll back a ** transaction. Nor will it be considered to be a hot-journal by this ** or any other database connection. Exactly how a journal is finalized ** depends on whether or not the pager is running in exclusive mode and ** the current journal-mode (Pager.journalMode value), as follows: ** ** journalMode==MEMORY ** Journal file descriptor is simply closed. This destroys an ** in-memory journal. ** ** journalMode==TRUNCATE ** Journal file is truncated to zero bytes in size. ** ** journalMode==PERSIST ** The first 28 bytes of the journal file are zeroed. This invalidates ** the first journal header in the file, and hence the entire journal ** file. An invalid journal file cannot be rolled back. ** ** journalMode==DELETE ** The journal file is closed and deleted using sqlite3OsDelete(). ** ** If the pager is running in exclusive mode, this method of finalizing ** the journal file is never used. Instead, if the journalMode is ** DELETE and the pager is in exclusive mode, the method described under ** journalMode==PERSIST is used instead. ** ** After the journal is finalized, the pager moves to PAGER_READER state. ** If running in non-exclusive rollback mode, the lock on the file is ** downgraded to a SHARED_LOCK. ** ** SQLITE_OK is returned if no error occurs. If an error occurs during ** any of the IO operations to finalize the journal file or unlock the ** database then the IO error code is returned to the user. If the ** operation to finalize the journal file fails, then the code still ** tries to unlock the database file if not in exclusive mode. If the ** unlock operation fails as well, then the first error code related ** to the first error encountered (the journal finalization one) is ** returned. */ static int pager_end_transaction(Pager *pPager, int hasSuper, int bCommit){ int rc = SQLITE_OK; /* Error code from journal finalization operation */ int rc2 = SQLITE_OK; /* Error code from db file unlock operation */ /* Do nothing if the pager does not have an open write transaction ** or at least a RESERVED lock. This function may be called when there ** is no write-transaction active but a RESERVED or greater lock is ** held under two circumstances: ** ** 1. After a successful hot-journal rollback, it is called with ** eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK. ** ** 2. If a connection with locking_mode=exclusive holding an EXCLUSIVE ** lock switches back to locking_mode=normal and then executes a ** read-transaction, this function is called with eState==PAGER_READER ** and eLock==EXCLUSIVE_LOCK when the read-transaction is closed. */ assert( assert_pager_state(pPager) ); assert( pPager->eState!=PAGER_ERROR ); if( pPager->eStateeLockjfd) || pPager->pInJournal==0 || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_BATCH_ATOMIC) ); if( isOpen(pPager->jfd) ){ assert( !pagerUseWal(pPager) ); /* Finalize the journal file. */ if( sqlite3JournalIsInMemory(pPager->jfd) ){ /* assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ); */ sqlite3OsClose(pPager->jfd); }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){ if( pPager->journalOff==0 ){ rc = SQLITE_OK; }else{ rc = sqlite3OsTruncate(pPager->jfd, 0); if( rc==SQLITE_OK && pPager->fullSync ){ /* Make sure the new file size is written into the inode right away. ** Otherwise the journal might resurrect following a power loss and ** cause the last transaction to roll back. See ** https://bugzilla.mozilla.org/show_bug.cgi?id=1072773 */ rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags); } } pPager->journalOff = 0; }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL) ){ rc = zeroJournalHdr(pPager, hasSuper||pPager->tempFile); pPager->journalOff = 0; }else{ /* This branch may be executed with Pager.journalMode==MEMORY if ** a hot-journal was just rolled back. In this case the journal ** file should be closed and deleted. If this connection writes to ** the database file, it will do so using an in-memory journal. */ int bDelete = !pPager->tempFile; assert( sqlite3JournalIsInMemory(pPager->jfd)==0 ); assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE || pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->journalMode==PAGER_JOURNALMODE_WAL ); sqlite3OsClose(pPager->jfd); if( bDelete ){ rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, pPager->extraSync); } } } #ifdef SQLITE_CHECK_PAGES sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash); if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){ PgHdr *p = sqlite3PagerLookup(pPager, 1); if( p ){ p->pageHash = 0; sqlite3PagerUnrefNotNull(p); } } #endif sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; pPager->nRec = 0; if( rc==SQLITE_OK ){ if( MEMDB || pagerFlushOnCommit(pPager, bCommit) ){ sqlite3PcacheCleanAll(pPager->pPCache); }else{ sqlite3PcacheClearWritable(pPager->pPCache); } sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize); } if( pagerUseWal(pPager) ){ /* Drop the WAL write-lock, if any. Also, if the connection was in ** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE ** lock held on the database file. */ rc2 = sqlite3WalEndWriteTransaction(pPager->pWal); assert( rc2==SQLITE_OK ); }else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){ /* This branch is taken when committing a transaction in rollback-journal ** mode if the database file on disk is larger than the database image. ** At this point the journal has been finalized and the transaction ** successfully committed, but the EXCLUSIVE lock is still held on the ** file. So it is safe to truncate the database file to its minimum ** required size. */ assert( pPager->eLock==EXCLUSIVE_LOCK ); rc = pager_truncate(pPager, pPager->dbSize); } if( rc==SQLITE_OK && bCommit ){ rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0); if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK; } if( !pPager->exclusiveMode && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0)) ){ rc2 = pagerUnlockDb(pPager, SHARED_LOCK); } pPager->eState = PAGER_READER; pPager->setSuper = 0; return (rc==SQLITE_OK?rc2:rc); } /* ** Execute a rollback if a transaction is active and unlock the ** database file. ** ** If the pager has already entered the ERROR state, do not attempt ** the rollback at this time. Instead, pager_unlock() is called. The ** call to pager_unlock() will discard all in-memory pages, unlock ** the database file and move the pager back to OPEN state. If this ** means that there is a hot-journal left in the file-system, the next ** connection to obtain a shared lock on the pager (which may be this one) ** will roll it back. ** ** If the pager has not already entered the ERROR state, but an IO or ** malloc error occurs during a rollback, then this will itself cause ** the pager to enter the ERROR state. Which will be cleared by the ** call to pager_unlock(), as described above. */ static void pagerUnlockAndRollback(Pager *pPager){ if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){ assert( assert_pager_state(pPager) ); if( pPager->eState>=PAGER_WRITER_LOCKED ){ sqlite3BeginBenignMalloc(); sqlite3PagerRollback(pPager); sqlite3EndBenignMalloc(); }else if( !pPager->exclusiveMode ){ assert( pPager->eState==PAGER_READER ); pager_end_transaction(pPager, 0, 0); } } pager_unlock(pPager); } /* ** Parameter aData must point to a buffer of pPager->pageSize bytes ** of data. Compute and return a checksum based ont the contents of the ** page of data and the current value of pPager->cksumInit. ** ** This is not a real checksum. It is really just the sum of the ** random initial value (pPager->cksumInit) and every 200th byte ** of the page data, starting with byte offset (pPager->pageSize%200). ** Each byte is interpreted as an 8-bit unsigned integer. ** ** Changing the formula used to compute this checksum results in an ** incompatible journal file format. ** ** If journal corruption occurs due to a power failure, the most likely ** scenario is that one end or the other of the record will be changed. ** It is much less likely that the two ends of the journal record will be ** correct and the middle be corrupt. Thus, this "checksum" scheme, ** though fast and simple, catches the mostly likely kind of corruption. */ static u32 pager_cksum(Pager *pPager, const u8 *aData){ u32 cksum = pPager->cksumInit; /* Checksum value to return */ int i = pPager->pageSize-200; /* Loop counter */ while( i>0 ){ cksum += aData[i]; i -= 200; } return cksum; } /* ** Read a single page from either the journal file (if isMainJrnl==1) or ** from the sub-journal (if isMainJrnl==0) and playback that page. ** The page begins at offset *pOffset into the file. The *pOffset ** value is increased to the start of the next page in the journal. ** ** The main rollback journal uses checksums - the statement journal does ** not. ** ** If the page number of the page record read from the (sub-)journal file ** is greater than the current value of Pager.dbSize, then playback is ** skipped and SQLITE_OK is returned. ** ** If pDone is not NULL, then it is a record of pages that have already ** been played back. If the page at *pOffset has already been played back ** (if the corresponding pDone bit is set) then skip the playback. ** Make sure the pDone bit corresponding to the *pOffset page is set ** prior to returning. ** ** If the page record is successfully read from the (sub-)journal file ** and played back, then SQLITE_OK is returned. If an IO error occurs ** while reading the record from the (sub-)journal file or while writing ** to the database file, then the IO error code is returned. If data ** is successfully read from the (sub-)journal file but appears to be ** corrupted, SQLITE_DONE is returned. Data is considered corrupted in ** two circumstances: ** ** * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or ** * If the record is being rolled back from the main journal file ** and the checksum field does not match the record content. ** ** Neither of these two scenarios are possible during a savepoint rollback. ** ** If this is a savepoint rollback, then memory may have to be dynamically ** allocated by this function. If this is the case and an allocation fails, ** SQLITE_NOMEM is returned. */ static int pager_playback_one_page( Pager *pPager, /* The pager being played back */ i64 *pOffset, /* Offset of record to playback */ Bitvec *pDone, /* Bitvec of pages already played back */ int isMainJrnl, /* 1 -> main journal. 0 -> sub-journal. */ int isSavepnt /* True for a savepoint rollback */ ){ int rc; PgHdr *pPg; /* An existing page in the cache */ Pgno pgno; /* The page number of a page in journal */ u32 cksum; /* Checksum used for sanity checking */ char *aData; /* Temporary storage for the page */ sqlite3_file *jfd; /* The file descriptor for the journal file */ int isSynced; /* True if journal page is synced */ assert( (isMainJrnl&~1)==0 ); /* isMainJrnl is 0 or 1 */ assert( (isSavepnt&~1)==0 ); /* isSavepnt is 0 or 1 */ assert( isMainJrnl || pDone ); /* pDone always used on sub-journals */ assert( isSavepnt || pDone==0 ); /* pDone never used on non-savepoint */ aData = pPager->pTmpSpace; assert( aData ); /* Temp storage must have already been allocated */ assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) ); /* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction ** or savepoint rollback done at the request of the caller) or this is ** a hot-journal rollback. If it is a hot-journal rollback, the pager ** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback ** only reads from the main journal, not the sub-journal. */ assert( pPager->eState>=PAGER_WRITER_CACHEMOD || (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK) ); assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl ); /* Read the page number and page data from the journal or sub-journal ** file. Return an error code to the caller if an IO error occurs. */ jfd = isMainJrnl ? pPager->jfd : pPager->sjfd; rc = read32bits(jfd, *pOffset, &pgno); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4); if( rc!=SQLITE_OK ) return rc; *pOffset += pPager->pageSize + 4 + isMainJrnl*4; /* Sanity checking on the page. This is more important that I originally ** thought. If a power failure occurs while the journal is being written, ** it could cause invalid data to be written into the journal. We need to ** detect this invalid data (with high probability) and ignore it. */ if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){ assert( !isSavepnt ); return SQLITE_DONE; } if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){ return SQLITE_OK; } if( isMainJrnl ){ rc = read32bits(jfd, (*pOffset)-4, &cksum); if( rc ) return rc; if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){ return SQLITE_DONE; } } /* If this page has already been played back before during the current ** rollback, then don't bother to play it back again. */ if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){ return rc; } /* When playing back page 1, restore the nReserve setting */ if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){ pPager->nReserve = ((u8*)aData)[20]; } /* If the pager is in CACHEMOD state, then there must be a copy of this ** page in the pager cache. In this case just update the pager cache, ** not the database file. The page is left marked dirty in this case. ** ** An exception to the above rule: If the database is in no-sync mode ** and a page is moved during an incremental vacuum then the page may ** not be in the pager cache. Later: if a malloc() or IO error occurs ** during a Movepage() call, then the page may not be in the cache ** either. So the condition described in the above paragraph is not ** assert()able. ** ** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the ** pager cache if it exists and the main file. The page is then marked ** not dirty. Since this code is only executed in PAGER_OPEN state for ** a hot-journal rollback, it is guaranteed that the page-cache is empty ** if the pager is in OPEN state. ** ** Ticket #1171: The statement journal might contain page content that is ** different from the page content at the start of the transaction. ** This occurs when a page is changed prior to the start of a statement ** then changed again within the statement. When rolling back such a ** statement we must not write to the original database unless we know ** for certain that original page contents are synced into the main rollback ** journal. Otherwise, a power loss might leave modified data in the ** database file without an entry in the rollback journal that can ** restore the database to its original form. Two conditions must be ** met before writing to the database files. (1) the database must be ** locked. (2) we know that the original page content is fully synced ** in the main journal either because the page is not in cache or else ** the page is marked as needSync==0. ** ** 2008-04-14: When attempting to vacuum a corrupt database file, it ** is possible to fail a statement on a database that does not yet exist. ** Do not attempt to write if database file has never been opened. */ if( pagerUseWal(pPager) ){ pPg = 0; }else{ pPg = sqlite3PagerLookup(pPager, pgno); } assert( pPg || !MEMDB ); assert( pPager->eState!=PAGER_OPEN || pPg==0 || pPager->tempFile ); PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n", PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData), (isMainJrnl?"main-journal":"sub-journal") )); if( isMainJrnl ){ isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr); }else{ isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC)); } if( isOpen(pPager->fd) && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) && isSynced ){ i64 ofst = (pgno-1)*(i64)pPager->pageSize; testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 ); assert( !pagerUseWal(pPager) ); /* Write the data read from the journal back into the database file. ** This is usually safe even for an encrypted database - as the data ** was encrypted before it was written to the journal file. The exception ** is if the data was just read from an in-memory sub-journal. In that ** case it must be encrypted here before it is copied into the database ** file. */ rc = sqlite3OsWrite(pPager->fd, (u8 *)aData, pPager->pageSize, ofst); if( pgno>pPager->dbFileSize ){ pPager->dbFileSize = pgno; } if( pPager->pBackup ){ sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData); } }else if( !isMainJrnl && pPg==0 ){ /* If this is a rollback of a savepoint and data was not written to ** the database and the page is not in-memory, there is a potential ** problem. When the page is next fetched by the b-tree layer, it ** will be read from the database file, which may or may not be ** current. ** ** There are a couple of different ways this can happen. All are quite ** obscure. When running in synchronous mode, this can only happen ** if the page is on the free-list at the start of the transaction, then ** populated, then moved using sqlite3PagerMovepage(). ** ** The solution is to add an in-memory page to the cache containing ** the data just read from the sub-journal. Mark the page as dirty ** and if the pager requires a journal-sync, then mark the page as ** requiring a journal-sync before it is written. */ assert( isSavepnt ); assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)==0 ); pPager->doNotSpill |= SPILLFLAG_ROLLBACK; rc = sqlite3PagerGet(pPager, pgno, &pPg, 1); assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 ); pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK; if( rc!=SQLITE_OK ) return rc; sqlite3PcacheMakeDirty(pPg); } if( pPg ){ /* No page should ever be explicitly rolled back that is in use, except ** for page 1 which is held in use in order to keep the lock on the ** database active. However such a page may be rolled back as a result ** of an internal error resulting in an automatic call to ** sqlite3PagerRollback(). */ void *pData; pData = pPg->pData; memcpy(pData, (u8*)aData, pPager->pageSize); pPager->xReiniter(pPg); /* It used to be that sqlite3PcacheMakeClean(pPg) was called here. But ** that call was dangerous and had no detectable benefit since the cache ** is normally cleaned by sqlite3PcacheCleanAll() after rollback and so ** has been removed. */ pager_set_pagehash(pPg); /* If this was page 1, then restore the value of Pager.dbFileVers. ** Do this before any decoding. */ if( pgno==1 ){ memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers)); } sqlite3PcacheRelease(pPg); } return rc; } /* ** Parameter zSuper is the name of a super-journal file. A single journal ** file that referred to the super-journal file has just been rolled back. ** This routine checks if it is possible to delete the super-journal file, ** and does so if it is. ** ** Argument zSuper may point to Pager.pTmpSpace. So that buffer is not ** available for use within this function. ** ** When a super-journal file is created, it is populated with the names ** of all of its child journals, one after another, formatted as utf-8 ** encoded text. The end of each child journal file is marked with a ** nul-terminator byte (0x00). i.e. the entire contents of a super-journal ** file for a transaction involving two databases might be: ** ** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00" ** ** A super-journal file may only be deleted once all of its child ** journals have been rolled back. ** ** This function reads the contents of the super-journal file into ** memory and loops through each of the child journal names. For ** each child journal, it checks if: ** ** * if the child journal exists, and if so ** * if the child journal contains a reference to super-journal ** file zSuper ** ** If a child journal can be found that matches both of the criteria ** above, this function returns without doing anything. Otherwise, if ** no such child journal can be found, file zSuper is deleted from ** the file-system using sqlite3OsDelete(). ** ** If an IO error within this function, an error code is returned. This ** function allocates memory by calling sqlite3Malloc(). If an allocation ** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors ** occur, SQLITE_OK is returned. ** ** TODO: This function allocates a single block of memory to load ** the entire contents of the super-journal file. This could be ** a couple of kilobytes or so - potentially larger than the page ** size. */ static int pager_delsuper(Pager *pPager, const char *zSuper){ sqlite3_vfs *pVfs = pPager->pVfs; int rc; /* Return code */ sqlite3_file *pSuper; /* Malloc'd super-journal file descriptor */ sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */ char *zSuperJournal = 0; /* Contents of super-journal file */ i64 nSuperJournal; /* Size of super-journal file */ char *zJournal; /* Pointer to one journal within MJ file */ char *zSuperPtr; /* Space to hold super-journal filename */ char *zFree = 0; /* Free this buffer */ int nSuperPtr; /* Amount of space allocated to zSuperPtr[] */ /* Allocate space for both the pJournal and pSuper file descriptors. ** If successful, open the super-journal file for reading. */ pSuper = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2); if( !pSuper ){ rc = SQLITE_NOMEM_BKPT; pJournal = 0; }else{ const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL); rc = sqlite3OsOpen(pVfs, zSuper, pSuper, flags, 0); pJournal = (sqlite3_file *)(((u8 *)pSuper) + pVfs->szOsFile); } if( rc!=SQLITE_OK ) goto delsuper_out; /* Load the entire super-journal file into space obtained from ** sqlite3_malloc() and pointed to by zSuperJournal. Also obtain ** sufficient space (in zSuperPtr) to hold the names of super-journal ** files extracted from regular rollback-journals. */ rc = sqlite3OsFileSize(pSuper, &nSuperJournal); if( rc!=SQLITE_OK ) goto delsuper_out; nSuperPtr = pVfs->mxPathname+1; zFree = sqlite3Malloc(4 + nSuperJournal + nSuperPtr + 2); if( !zFree ){ rc = SQLITE_NOMEM_BKPT; goto delsuper_out; } zFree[0] = zFree[1] = zFree[2] = zFree[3] = 0; zSuperJournal = &zFree[4]; zSuperPtr = &zSuperJournal[nSuperJournal+2]; rc = sqlite3OsRead(pSuper, zSuperJournal, (int)nSuperJournal, 0); if( rc!=SQLITE_OK ) goto delsuper_out; zSuperJournal[nSuperJournal] = 0; zSuperJournal[nSuperJournal+1] = 0; zJournal = zSuperJournal; while( (zJournal-zSuperJournal)pageSize bytes). ** If the file on disk is currently larger than nPage pages, then use the VFS ** xTruncate() method to truncate it. ** ** Or, it might be the case that the file on disk is smaller than ** nPage pages. Some operating system implementations can get confused if ** you try to truncate a file to some size that is larger than it ** currently is, so detect this case and write a single zero byte to ** the end of the new file instead. ** ** If successful, return SQLITE_OK. If an IO error occurs while modifying ** the database file, return the error code to the caller. */ static int pager_truncate(Pager *pPager, Pgno nPage){ int rc = SQLITE_OK; assert( pPager->eState!=PAGER_ERROR ); assert( pPager->eState!=PAGER_READER ); if( isOpen(pPager->fd) && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) ){ i64 currentSize, newSize; int szPage = pPager->pageSize; assert( pPager->eLock==EXCLUSIVE_LOCK ); /* TODO: Is it safe to use Pager.dbFileSize here? */ rc = sqlite3OsFileSize(pPager->fd, ¤tSize); newSize = szPage*(i64)nPage; if( rc==SQLITE_OK && currentSize!=newSize ){ if( currentSize>newSize ){ rc = sqlite3OsTruncate(pPager->fd, newSize); }else if( (currentSize+szPage)<=newSize ){ char *pTmp = pPager->pTmpSpace; memset(pTmp, 0, szPage); testcase( (newSize-szPage) == currentSize ); testcase( (newSize-szPage) > currentSize ); rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage); } if( rc==SQLITE_OK ){ pPager->dbFileSize = nPage; } } } return rc; } /* ** Return a sanitized version of the sector-size of OS file pFile. The ** return value is guaranteed to lie between 32 and MAX_SECTOR_SIZE. */ int sqlite3SectorSize(sqlite3_file *pFile){ int iRet = sqlite3OsSectorSize(pFile); if( iRet<32 ){ iRet = 512; }else if( iRet>MAX_SECTOR_SIZE ){ assert( MAX_SECTOR_SIZE>=512 ); iRet = MAX_SECTOR_SIZE; } return iRet; } /* ** Set the value of the Pager.sectorSize variable for the given ** pager based on the value returned by the xSectorSize method ** of the open database file. The sector size will be used ** to determine the size and alignment of journal header and ** super-journal pointers within created journal files. ** ** For temporary files the effective sector size is always 512 bytes. ** ** Otherwise, for non-temporary files, the effective sector size is ** the value returned by the xSectorSize() method rounded up to 32 if ** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it ** is greater than MAX_SECTOR_SIZE. ** ** If the file has the SQLITE_IOCAP_POWERSAFE_OVERWRITE property, then set ** the effective sector size to its minimum value (512). The purpose of ** pPager->sectorSize is to define the "blast radius" of bytes that ** might change if a crash occurs while writing to a single byte in ** that range. But with POWERSAFE_OVERWRITE, the blast radius is zero ** (that is what POWERSAFE_OVERWRITE means), so we minimize the sector ** size. For backwards compatibility of the rollback journal file format, ** we cannot reduce the effective sector size below 512. */ static void setSectorSize(Pager *pPager){ assert( isOpen(pPager->fd) || pPager->tempFile ); if( pPager->tempFile || (sqlite3OsDeviceCharacteristics(pPager->fd) & SQLITE_IOCAP_POWERSAFE_OVERWRITE)!=0 ){ /* Sector size doesn't matter for temporary files. Also, the file ** may not have been opened yet, in which case the OsSectorSize() ** call will segfault. */ pPager->sectorSize = 512; }else{ pPager->sectorSize = sqlite3SectorSize(pPager->fd); } } /* ** Playback the journal and thus restore the database file to ** the state it was in before we started making changes. ** ** The journal file format is as follows: ** ** (1) 8 byte prefix. A copy of aJournalMagic[]. ** (2) 4 byte big-endian integer which is the number of valid page records ** in the journal. If this value is 0xffffffff, then compute the ** number of page records from the journal size. ** (3) 4 byte big-endian integer which is the initial value for the ** sanity checksum. ** (4) 4 byte integer which is the number of pages to truncate the ** database to during a rollback. ** (5) 4 byte big-endian integer which is the sector size. The header ** is this many bytes in size. ** (6) 4 byte big-endian integer which is the page size. ** (7) zero padding out to the next sector size. ** (8) Zero or more pages instances, each as follows: ** + 4 byte page number. ** + pPager->pageSize bytes of data. ** + 4 byte checksum ** ** When we speak of the journal header, we mean the first 7 items above. ** Each entry in the journal is an instance of the 8th item. ** ** Call the value from the second bullet "nRec". nRec is the number of ** valid page entries in the journal. In most cases, you can compute the ** value of nRec from the size of the journal file. But if a power ** failure occurred while the journal was being written, it could be the ** case that the size of the journal file had already been increased but ** the extra entries had not yet made it safely to disk. In such a case, ** the value of nRec computed from the file size would be too large. For ** that reason, we always use the nRec value in the header. ** ** If the nRec value is 0xffffffff it means that nRec should be computed ** from the file size. This value is used when the user selects the ** no-sync option for the journal. A power failure could lead to corruption ** in this case. But for things like temporary table (which will be ** deleted when the power is restored) we don't care. ** ** If the file opened as the journal file is not a well-formed ** journal file then all pages up to the first corrupted page are rolled ** back (or no pages if the journal header is corrupted). The journal file ** is then deleted and SQLITE_OK returned, just as if no corruption had ** been encountered. ** ** If an I/O or malloc() error occurs, the journal-file is not deleted ** and an error code is returned. ** ** The isHot parameter indicates that we are trying to rollback a journal ** that might be a hot journal. Or, it could be that the journal is ** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE. ** If the journal really is hot, reset the pager cache prior rolling ** back any content. If the journal is merely persistent, no reset is ** needed. */ static int pager_playback(Pager *pPager, int isHot){ sqlite3_vfs *pVfs = pPager->pVfs; i64 szJ; /* Size of the journal file in bytes */ u32 nRec; /* Number of Records in the journal */ u32 u; /* Unsigned loop counter */ Pgno mxPg = 0; /* Size of the original file in pages */ int rc; /* Result code of a subroutine */ int res = 1; /* Value returned by sqlite3OsAccess() */ char *zSuper = 0; /* Name of super-journal file if any */ int needPagerReset; /* True to reset page prior to first page rollback */ int nPlayback = 0; /* Total number of pages restored from journal */ u32 savedPageSize = pPager->pageSize; /* Figure out how many records are in the journal. Abort early if ** the journal is empty. */ assert( isOpen(pPager->jfd) ); rc = sqlite3OsFileSize(pPager->jfd, &szJ); if( rc!=SQLITE_OK ){ goto end_playback; } /* Read the super-journal name from the journal, if it is present. ** If a super-journal file name is specified, but the file is not ** present on disk, then the journal is not hot and does not need to be ** played back. ** ** TODO: Technically the following is an error because it assumes that ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c, ** mxPathname is 512, which is the same as the minimum allowable value ** for pageSize. */ zSuper = pPager->pTmpSpace; rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1); if( rc==SQLITE_OK && zSuper[0] ){ rc = sqlite3OsAccess(pVfs, zSuper, SQLITE_ACCESS_EXISTS, &res); } zSuper = 0; if( rc!=SQLITE_OK || !res ){ goto end_playback; } pPager->journalOff = 0; needPagerReset = isHot; /* This loop terminates either when a readJournalHdr() or ** pager_playback_one_page() call returns SQLITE_DONE or an IO error ** occurs. */ while( 1 ){ /* Read the next journal header from the journal file. If there are ** not enough bytes left in the journal file for a complete header, or ** it is corrupted, then a process must have failed while writing it. ** This indicates nothing more needs to be rolled back. */ rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg); if( rc!=SQLITE_OK ){ if( rc==SQLITE_DONE ){ rc = SQLITE_OK; } goto end_playback; } /* If nRec is 0xffffffff, then this journal was created by a process ** working in no-sync mode. This means that the rest of the journal ** file consists of pages, there are no more journal headers. Compute ** the value of nRec based on this assumption. */ if( nRec==0xffffffff ){ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ); nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager)); } /* If nRec is 0 and this rollback is of a transaction created by this ** process and if this is the final header in the journal, then it means ** that this part of the journal was being filled but has not yet been ** synced to disk. Compute the number of pages based on the remaining ** size of the file. ** ** The third term of the test was added to fix ticket #2565. ** When rolling back a hot journal, nRec==0 always means that the next ** chunk of the journal contains zero pages to be rolled back. But ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in ** the journal, it means that the journal might contain additional ** pages that need to be rolled back and that the number of pages ** should be computed based on the journal file size. */ if( nRec==0 && !isHot && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){ nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager)); } /* If this is the first header read from the journal, truncate the ** database file back to its original size. */ if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){ rc = pager_truncate(pPager, mxPg); if( rc!=SQLITE_OK ){ goto end_playback; } pPager->dbSize = mxPg; } /* Copy original pages out of the journal and back into the ** database file and/or page cache. */ for(u=0; ujournalOff,0,1,0); if( rc==SQLITE_OK ){ nPlayback++; }else{ if( rc==SQLITE_DONE ){ pPager->journalOff = szJ; break; }else if( rc==SQLITE_IOERR_SHORT_READ ){ /* If the journal has been truncated, simply stop reading and ** processing the journal. This might happen if the journal was ** not completely written and synced prior to a crash. In that ** case, the database should have never been written in the ** first place so it is OK to simply abandon the rollback. */ rc = SQLITE_OK; goto end_playback; }else{ /* If we are unable to rollback, quit and return the error ** code. This will cause the pager to enter the error state ** so that no further harm will be done. Perhaps the next ** process to come along will be able to rollback the database. */ goto end_playback; } } } } /*NOTREACHED*/ assert( 0 ); end_playback: if( rc==SQLITE_OK ){ rc = sqlite3PagerSetPagesize(pPager, &savedPageSize, -1); } /* Following a rollback, the database file should be back in its original ** state prior to the start of the transaction, so invoke the ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the ** assertion that the transaction counter was modified. */ #ifdef SQLITE_DEBUG sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0); #endif /* If this playback is happening automatically as a result of an IO or ** malloc error that occurred after the change-counter was updated but ** before the transaction was committed, then the change-counter ** modification may just have been reverted. If this happens in exclusive ** mode, then subsequent transactions performed by the connection will not ** update the change-counter at all. This may lead to cache inconsistency ** problems for other processes at some point in the future. So, just ** in case this has happened, clear the changeCountDone flag now. */ pPager->changeCountDone = pPager->tempFile; if( rc==SQLITE_OK ){ /* Leave 4 bytes of space before the super-journal filename in memory. ** This is because it may end up being passed to sqlite3OsOpen(), in ** which case it requires 4 0x00 bytes in memory immediately before ** the filename. */ zSuper = &pPager->pTmpSpace[4]; rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1); testcase( rc!=SQLITE_OK ); } if( rc==SQLITE_OK && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) ){ rc = sqlite3PagerSync(pPager, 0); } if( rc==SQLITE_OK ){ rc = pager_end_transaction(pPager, zSuper[0]!='\0', 0); testcase( rc!=SQLITE_OK ); } if( rc==SQLITE_OK && zSuper[0] && res ){ /* If there was a super-journal and this routine will return success, ** see if it is possible to delete the super-journal. */ assert( zSuper==&pPager->pTmpSpace[4] ); memset(&zSuper[-4], 0, 4); rc = pager_delsuper(pPager, zSuper); testcase( rc!=SQLITE_OK ); } if( isHot && nPlayback ){ sqlite3_log(SQLITE_NOTICE_RECOVER_ROLLBACK, "recovered %d pages from %s", nPlayback, pPager->zJournal); } /* The Pager.sectorSize variable may have been updated while rolling ** back a journal created by a process with a different sector size ** value. Reset it to the correct value for this process. */ setSectorSize(pPager); return rc; } /* ** Read the content for page pPg out of the database file (or out of ** the WAL if that is where the most recent copy if found) into ** pPg->pData. A shared lock or greater must be held on the database ** file before this function is called. ** ** If page 1 is read, then the value of Pager.dbFileVers[] is set to ** the value read from the database file. ** ** If an IO error occurs, then the IO error is returned to the caller. ** Otherwise, SQLITE_OK is returned. */ static int readDbPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */ int rc = SQLITE_OK; /* Return code */ #ifndef SQLITE_OMIT_WAL u32 iFrame = 0; /* Frame of WAL containing pgno */ assert( pPager->eState>=PAGER_READER && !MEMDB ); assert( isOpen(pPager->fd) ); if( pagerUseWal(pPager) ){ rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame); if( rc ) return rc; } if( iFrame ){ rc = sqlite3WalReadFrame(pPager->pWal, iFrame,pPager->pageSize,pPg->pData); }else #endif { i64 iOffset = (pPg->pgno-1)*(i64)pPager->pageSize; rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } } if( pPg->pgno==1 ){ if( rc ){ /* If the read is unsuccessful, set the dbFileVers[] to something ** that will never be a valid file version. dbFileVers[] is a copy ** of bytes 24..39 of the database. Bytes 28..31 should always be ** zero or the size of the database in page. Bytes 32..35 and 35..39 ** should be page numbers which are never 0xffffffff. So filling ** pPager->dbFileVers[] with all 0xff bytes should suffice. ** ** For an encrypted database, the situation is more complex: bytes ** 24..39 of the database are white noise. But the probability of ** white noise equaling 16 bytes of 0xff is vanishingly small so ** we should still be ok. */ memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers)); }else{ u8 *dbFileVers = &((u8*)pPg->pData)[24]; memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers)); } } PAGER_INCR(sqlite3_pager_readdb_count); PAGER_INCR(pPager->nRead); IOTRACE(("PGIN %p %d\n", pPager, pPg->pgno)); PAGERTRACE(("FETCH %d page %d hash(%08x)\n", PAGERID(pPager), pPg->pgno, pager_pagehash(pPg))); return rc; } /* ** Update the value of the change-counter at offsets 24 and 92 in ** the header and the sqlite version number at offset 96. ** ** This is an unconditional update. See also the pager_incr_changecounter() ** routine which only updates the change-counter if the update is actually ** needed, as determined by the pPager->changeCountDone state variable. */ static void pager_write_changecounter(PgHdr *pPg){ u32 change_counter; if( NEVER(pPg==0) ) return; /* Increment the value just read and write it back to byte 24. */ change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1; put32bits(((char*)pPg->pData)+24, change_counter); /* Also store the SQLite version number in bytes 96..99 and in ** bytes 92..95 store the change counter for which the version number ** is valid. */ put32bits(((char*)pPg->pData)+92, change_counter); put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER); } #ifndef SQLITE_OMIT_WAL /* ** This function is invoked once for each page that has already been ** written into the log file when a WAL transaction is rolled back. ** Parameter iPg is the page number of said page. The pCtx argument ** is actually a pointer to the Pager structure. ** ** If page iPg is present in the cache, and has no outstanding references, ** it is discarded. Otherwise, if there are one or more outstanding ** references, the page content is reloaded from the database. If the ** attempt to reload content from the database is required and fails, ** return an SQLite error code. Otherwise, SQLITE_OK. */ static int pagerUndoCallback(void *pCtx, Pgno iPg){ int rc = SQLITE_OK; Pager *pPager = (Pager *)pCtx; PgHdr *pPg; assert( pagerUseWal(pPager) ); pPg = sqlite3PagerLookup(pPager, iPg); if( pPg ){ if( sqlite3PcachePageRefcount(pPg)==1 ){ sqlite3PcacheDrop(pPg); }else{ rc = readDbPage(pPg); if( rc==SQLITE_OK ){ pPager->xReiniter(pPg); } sqlite3PagerUnrefNotNull(pPg); } } /* Normally, if a transaction is rolled back, any backup processes are ** updated as data is copied out of the rollback journal and into the ** database. This is not generally possible with a WAL database, as ** rollback involves simply truncating the log file. Therefore, if one ** or more frames have already been written to the log (and therefore ** also copied into the backup databases) as part of this transaction, ** the backups must be restarted. */ sqlite3BackupRestart(pPager->pBackup); return rc; } /* ** This function is called to rollback a transaction on a WAL database. */ static int pagerRollbackWal(Pager *pPager){ int rc; /* Return Code */ PgHdr *pList; /* List of dirty pages to revert */ /* For all pages in the cache that are currently dirty or have already ** been written (but not committed) to the log file, do one of the ** following: ** ** + Discard the cached page (if refcount==0), or ** + Reload page content from the database (if refcount>0). */ pPager->dbSize = pPager->dbOrigSize; rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager); pList = sqlite3PcacheDirtyList(pPager->pPCache); while( pList && rc==SQLITE_OK ){ PgHdr *pNext = pList->pDirty; rc = pagerUndoCallback((void *)pPager, pList->pgno); pList = pNext; } return rc; } /* ** This function is a wrapper around sqlite3WalFrames(). As well as logging ** the contents of the list of pages headed by pList (connected by pDirty), ** this function notifies any active backup processes that the pages have ** changed. ** ** The list of pages passed into this routine is always sorted by page number. ** Hence, if page 1 appears anywhere on the list, it will be the first page. */ static int pagerWalFrames( Pager *pPager, /* Pager object */ PgHdr *pList, /* List of frames to log */ Pgno nTruncate, /* Database size after this commit */ int isCommit /* True if this is a commit */ ){ int rc; /* Return code */ int nList; /* Number of pages in pList */ PgHdr *p; /* For looping over pages */ assert( pPager->pWal ); assert( pList ); #ifdef SQLITE_DEBUG /* Verify that the page list is in accending order */ for(p=pList; p && p->pDirty; p=p->pDirty){ assert( p->pgno < p->pDirty->pgno ); } #endif assert( pList->pDirty==0 || isCommit ); if( isCommit ){ /* If a WAL transaction is being committed, there is no point in writing ** any pages with page numbers greater than nTruncate into the WAL file. ** They will never be read by any client. So remove them from the pDirty ** list here. */ PgHdr **ppNext = &pList; nList = 0; for(p=pList; (*ppNext = p)!=0; p=p->pDirty){ if( p->pgno<=nTruncate ){ ppNext = &p->pDirty; nList++; } } assert( pList ); }else{ nList = 1; } pPager->aStat[PAGER_STAT_WRITE] += nList; if( pList->pgno==1 ) pager_write_changecounter(pList); rc = sqlite3WalFrames(pPager->pWal, pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags ); if( rc==SQLITE_OK && pPager->pBackup ){ for(p=pList; p; p=p->pDirty){ sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData); } } #ifdef SQLITE_CHECK_PAGES pList = sqlite3PcacheDirtyList(pPager->pPCache); for(p=pList; p; p=p->pDirty){ pager_set_pagehash(p); } #endif return rc; } /* ** Begin a read transaction on the WAL. ** ** This routine used to be called "pagerOpenSnapshot()" because it essentially ** makes a snapshot of the database at the current point in time and preserves ** that snapshot for use by the reader in spite of concurrently changes by ** other writers or checkpointers. */ static int pagerBeginReadTransaction(Pager *pPager){ int rc; /* Return code */ int changed = 0; /* True if cache must be reset */ assert( pagerUseWal(pPager) ); assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER ); /* sqlite3WalEndReadTransaction() was not called for the previous ** transaction in locking_mode=EXCLUSIVE. So call it now. If we ** are in locking_mode=NORMAL and EndRead() was previously called, ** the duplicate call is harmless. */ sqlite3WalEndReadTransaction(pPager->pWal); rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed); if( rc!=SQLITE_OK || changed ){ pager_reset(pPager); if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0); } return rc; } #endif /* ** This function is called as part of the transition from PAGER_OPEN ** to PAGER_READER state to determine the size of the database file ** in pages (assuming the page size currently stored in Pager.pageSize). ** ** If no error occurs, SQLITE_OK is returned and the size of the database ** in pages is stored in *pnPage. Otherwise, an error code (perhaps ** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified. */ static int pagerPagecount(Pager *pPager, Pgno *pnPage){ Pgno nPage; /* Value to return via *pnPage */ /* Query the WAL sub-system for the database size. The WalDbsize() ** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or ** if the database size is not available. The database size is not ** available from the WAL sub-system if the log file is empty or ** contains no valid committed transactions. */ assert( pPager->eState==PAGER_OPEN ); assert( pPager->eLock>=SHARED_LOCK ); assert( isOpen(pPager->fd) ); assert( pPager->tempFile==0 ); nPage = sqlite3WalDbsize(pPager->pWal); /* If the number of pages in the database is not available from the ** WAL sub-system, determine the page count based on the size of ** the database file. If the size of the database file is not an ** integer multiple of the page-size, round up the result. */ if( nPage==0 && ALWAYS(isOpen(pPager->fd)) ){ i64 n = 0; /* Size of db file in bytes */ int rc = sqlite3OsFileSize(pPager->fd, &n); if( rc!=SQLITE_OK ){ return rc; } nPage = (Pgno)((n+pPager->pageSize-1) / pPager->pageSize); } /* If the current number of pages in the file is greater than the ** configured maximum pager number, increase the allowed limit so ** that the file can be read. */ if( nPage>pPager->mxPgno ){ pPager->mxPgno = (Pgno)nPage; } *pnPage = nPage; return SQLITE_OK; } #ifndef SQLITE_OMIT_WAL /* ** Check if the *-wal file that corresponds to the database opened by pPager ** exists if the database is not empy, or verify that the *-wal file does ** not exist (by deleting it) if the database file is empty. ** ** If the database is not empty and the *-wal file exists, open the pager ** in WAL mode. If the database is empty or if no *-wal file exists and ** if no error occurs, make sure Pager.journalMode is not set to ** PAGER_JOURNALMODE_WAL. ** ** Return SQLITE_OK or an error code. ** ** The caller must hold a SHARED lock on the database file to call this ** function. Because an EXCLUSIVE lock on the db file is required to delete ** a WAL on a none-empty database, this ensures there is no race condition ** between the xAccess() below and an xDelete() being executed by some ** other connection. */ static int pagerOpenWalIfPresent(Pager *pPager){ int rc = SQLITE_OK; assert( pPager->eState==PAGER_OPEN ); assert( pPager->eLock>=SHARED_LOCK ); if( !pPager->tempFile ){ int isWal; /* True if WAL file exists */ rc = sqlite3OsAccess( pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal ); if( rc==SQLITE_OK ){ if( isWal ){ Pgno nPage; /* Size of the database file */ rc = pagerPagecount(pPager, &nPage); if( rc ) return rc; if( nPage==0 ){ rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0); }else{ testcase( sqlite3PcachePagecount(pPager->pPCache)==0 ); rc = sqlite3PagerOpenWal(pPager, 0); } }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){ pPager->journalMode = PAGER_JOURNALMODE_DELETE; } } } return rc; } #endif /* ** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback ** the entire super-journal file. The case pSavepoint==NULL occurs when ** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction ** savepoint. ** ** When pSavepoint is not NULL (meaning a non-transaction savepoint is ** being rolled back), then the rollback consists of up to three stages, ** performed in the order specified: ** ** * Pages are played back from the main journal starting at byte ** offset PagerSavepoint.iOffset and continuing to ** PagerSavepoint.iHdrOffset, or to the end of the main journal ** file if PagerSavepoint.iHdrOffset is zero. ** ** * If PagerSavepoint.iHdrOffset is not zero, then pages are played ** back starting from the journal header immediately following ** PagerSavepoint.iHdrOffset to the end of the main journal file. ** ** * Pages are then played back from the sub-journal file, starting ** with the PagerSavepoint.iSubRec and continuing to the end of ** the journal file. ** ** Throughout the rollback process, each time a page is rolled back, the ** corresponding bit is set in a bitvec structure (variable pDone in the ** implementation below). This is used to ensure that a page is only ** rolled back the first time it is encountered in either journal. ** ** If pSavepoint is NULL, then pages are only played back from the main ** journal file. There is no need for a bitvec in this case. ** ** In either case, before playback commences the Pager.dbSize variable ** is reset to the value that it held at the start of the savepoint ** (or transaction). No page with a page-number greater than this value ** is played back. If one is encountered it is simply skipped. */ static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){ i64 szJ; /* Effective size of the main journal */ i64 iHdrOff; /* End of first segment of main-journal records */ int rc = SQLITE_OK; /* Return code */ Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */ assert( pPager->eState!=PAGER_ERROR ); assert( pPager->eState>=PAGER_WRITER_LOCKED ); /* Allocate a bitvec to use to store the set of pages rolled back */ if( pSavepoint ){ pDone = sqlite3BitvecCreate(pSavepoint->nOrig); if( !pDone ){ return SQLITE_NOMEM_BKPT; } } /* Set the database size back to the value it was before the savepoint ** being reverted was opened. */ pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize; pPager->changeCountDone = pPager->tempFile; if( !pSavepoint && pagerUseWal(pPager) ){ return pagerRollbackWal(pPager); } /* Use pPager->journalOff as the effective size of the main rollback ** journal. The actual file might be larger than this in ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST. But anything ** past pPager->journalOff is off-limits to us. */ szJ = pPager->journalOff; assert( pagerUseWal(pPager)==0 || szJ==0 ); /* Begin by rolling back records from the main journal starting at ** PagerSavepoint.iOffset and continuing to the next journal header. ** There might be records in the main journal that have a page number ** greater than the current database size (pPager->dbSize) but those ** will be skipped automatically. Pages are added to pDone as they ** are played back. */ if( pSavepoint && !pagerUseWal(pPager) ){ iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ; pPager->journalOff = pSavepoint->iOffset; while( rc==SQLITE_OK && pPager->journalOffjournalOff, pDone, 1, 1); } assert( rc!=SQLITE_DONE ); }else{ pPager->journalOff = 0; } /* Continue rolling back records out of the main journal starting at ** the first journal header seen and continuing until the effective end ** of the main journal file. Continue to skip out-of-range pages and ** continue adding pages rolled back to pDone. */ while( rc==SQLITE_OK && pPager->journalOffjournalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff" ** test is related to ticket #2565. See the discussion in the ** pager_playback() function for additional information. */ if( nJRec==0 && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){ nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager)); } for(ii=0; rc==SQLITE_OK && iijournalOffjournalOff, pDone, 1, 1); } assert( rc!=SQLITE_DONE ); } assert( rc!=SQLITE_OK || pPager->journalOff>=szJ ); /* Finally, rollback pages from the sub-journal. Page that were ** previously rolled back out of the main journal (and are hence in pDone) ** will be skipped. Out-of-range pages are also skipped. */ if( pSavepoint ){ u32 ii; /* Loop counter */ i64 offset = (i64)pSavepoint->iSubRec*(4+pPager->pageSize); if( pagerUseWal(pPager) ){ rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData); } for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && iinSubRec; ii++){ assert( offset==(i64)ii*(4+pPager->pageSize) ); rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1); } assert( rc!=SQLITE_DONE ); } sqlite3BitvecDestroy(pDone); if( rc==SQLITE_OK ){ pPager->journalOff = szJ; } return rc; } /* ** Change the maximum number of in-memory pages that are allowed ** before attempting to recycle clean and unused pages. */ void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){ sqlite3PcacheSetCachesize(pPager->pPCache, mxPage); } /* ** Change the maximum number of in-memory pages that are allowed ** before attempting to spill pages to journal. */ int sqlite3PagerSetSpillsize(Pager *pPager, int mxPage){ return sqlite3PcacheSetSpillsize(pPager->pPCache, mxPage); } /* ** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap. */ static void pagerFixMaplimit(Pager *pPager){ #if SQLITE_MAX_MMAP_SIZE>0 sqlite3_file *fd = pPager->fd; if( isOpen(fd) && fd->pMethods->iVersion>=3 ){ sqlite3_int64 sz; sz = pPager->szMmap; pPager->bUseFetch = (sz>0); setGetterMethod(pPager); sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz); } #endif } /* ** Change the maximum size of any memory mapping made of the database file. */ void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){ pPager->szMmap = szMmap; pagerFixMaplimit(pPager); } /* ** Free as much memory as possible from the pager. */ void sqlite3PagerShrink(Pager *pPager){ sqlite3PcacheShrink(pPager->pPCache); } /* ** Adjust settings of the pager to those specified in the pgFlags parameter. ** ** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness ** of the database to damage due to OS crashes or power failures by ** changing the number of syncs()s when writing the journals. ** There are four levels: ** ** OFF sqlite3OsSync() is never called. This is the default ** for temporary and transient files. ** ** NORMAL The journal is synced once before writes begin on the ** database. This is normally adequate protection, but ** it is theoretically possible, though very unlikely, ** that an inopertune power failure could leave the journal ** in a state which would cause damage to the database ** when it is rolled back. ** ** FULL The journal is synced twice before writes begin on the ** database (with some additional information - the nRec field ** of the journal header - being written in between the two ** syncs). If we assume that writing a ** single disk sector is atomic, then this mode provides ** assurance that the journal will not be corrupted to the ** point of causing damage to the database during rollback. ** ** EXTRA This is like FULL except that is also syncs the directory ** that contains the rollback journal after the rollback ** journal is unlinked. ** ** The above is for a rollback-journal mode. For WAL mode, OFF continues ** to mean that no syncs ever occur. NORMAL means that the WAL is synced ** prior to the start of checkpoint and that the database file is synced ** at the conclusion of the checkpoint if the entire content of the WAL ** was written back into the database. But no sync operations occur for ** an ordinary commit in NORMAL mode with WAL. FULL means that the WAL ** file is synced following each commit operation, in addition to the ** syncs associated with NORMAL. There is no difference between FULL ** and EXTRA for WAL mode. ** ** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL. The ** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync ** using fcntl(F_FULLFSYNC). SQLITE_SYNC_NORMAL means to do an ** ordinary fsync() call. There is no difference between SQLITE_SYNC_FULL ** and SQLITE_SYNC_NORMAL on platforms other than MacOSX. But the ** synchronous=FULL versus synchronous=NORMAL setting determines when ** the xSync primitive is called and is relevant to all platforms. ** ** Numeric values associated with these states are OFF==1, NORMAL=2, ** and FULL=3. */ #ifndef SQLITE_OMIT_PAGER_PRAGMAS void sqlite3PagerSetFlags( Pager *pPager, /* The pager to set safety level for */ unsigned pgFlags /* Various flags */ ){ unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK; if( pPager->tempFile ){ pPager->noSync = 1; pPager->fullSync = 0; pPager->extraSync = 0; }else{ pPager->noSync = level==PAGER_SYNCHRONOUS_OFF ?1:0; pPager->fullSync = level>=PAGER_SYNCHRONOUS_FULL ?1:0; pPager->extraSync = level==PAGER_SYNCHRONOUS_EXTRA ?1:0; } if( pPager->noSync ){ pPager->syncFlags = 0; }else if( pgFlags & PAGER_FULLFSYNC ){ pPager->syncFlags = SQLITE_SYNC_FULL; }else{ pPager->syncFlags = SQLITE_SYNC_NORMAL; } pPager->walSyncFlags = (pPager->syncFlags<<2); if( pPager->fullSync ){ pPager->walSyncFlags |= pPager->syncFlags; } if( (pgFlags & PAGER_CKPT_FULLFSYNC) && !pPager->noSync ){ pPager->walSyncFlags |= (SQLITE_SYNC_FULL<<2); } if( pgFlags & PAGER_CACHESPILL ){ pPager->doNotSpill &= ~SPILLFLAG_OFF; }else{ pPager->doNotSpill |= SPILLFLAG_OFF; } } #endif /* ** The following global variable is incremented whenever the library ** attempts to open a temporary file. This information is used for ** testing and analysis only. */ #ifdef SQLITE_TEST int sqlite3_opentemp_count = 0; #endif /* ** Open a temporary file. ** ** Write the file descriptor into *pFile. Return SQLITE_OK on success ** or some other error code if we fail. The OS will automatically ** delete the temporary file when it is closed. ** ** The flags passed to the VFS layer xOpen() call are those specified ** by parameter vfsFlags ORed with the following: ** ** SQLITE_OPEN_READWRITE ** SQLITE_OPEN_CREATE ** SQLITE_OPEN_EXCLUSIVE ** SQLITE_OPEN_DELETEONCLOSE */ static int pagerOpentemp( Pager *pPager, /* The pager object */ sqlite3_file *pFile, /* Write the file descriptor here */ int vfsFlags /* Flags passed through to the VFS */ ){ int rc; /* Return code */ #ifdef SQLITE_TEST sqlite3_opentemp_count++; /* Used for testing and analysis only */ #endif vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE; rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0); assert( rc!=SQLITE_OK || isOpen(pFile) ); return rc; } /* ** Set the busy handler function. ** ** The pager invokes the busy-handler if sqlite3OsLock() returns ** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock, ** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE ** lock. It does *not* invoke the busy handler when upgrading from ** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE ** (which occurs during hot-journal rollback). Summary: ** ** Transition | Invokes xBusyHandler ** -------------------------------------------------------- ** NO_LOCK -> SHARED_LOCK | Yes ** SHARED_LOCK -> RESERVED_LOCK | No ** SHARED_LOCK -> EXCLUSIVE_LOCK | No ** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes ** ** If the busy-handler callback returns non-zero, the lock is ** retried. If it returns zero, then the SQLITE_BUSY error is ** returned to the caller of the pager API function. */ void sqlite3PagerSetBusyHandler( Pager *pPager, /* Pager object */ int (*xBusyHandler)(void *), /* Pointer to busy-handler function */ void *pBusyHandlerArg /* Argument to pass to xBusyHandler */ ){ void **ap; pPager->xBusyHandler = xBusyHandler; pPager->pBusyHandlerArg = pBusyHandlerArg; ap = (void **)&pPager->xBusyHandler; assert( ((int(*)(void *))(ap[0]))==xBusyHandler ); assert( ap[1]==pBusyHandlerArg ); sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap); } /* ** Change the page size used by the Pager object. The new page size ** is passed in *pPageSize. ** ** If the pager is in the error state when this function is called, it ** is a no-op. The value returned is the error state error code (i.e. ** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL). ** ** Otherwise, if all of the following are true: ** ** * the new page size (value of *pPageSize) is valid (a power ** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and ** ** * there are no outstanding page references, and ** ** * the database is either not an in-memory database or it is ** an in-memory database that currently consists of zero pages. ** ** then the pager object page size is set to *pPageSize. ** ** If the page size is changed, then this function uses sqlite3PagerMalloc() ** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt ** fails, SQLITE_NOMEM is returned and the page size remains unchanged. ** In all other cases, SQLITE_OK is returned. ** ** If the page size is not changed, either because one of the enumerated ** conditions above is not true, the pager was in error state when this ** function was called, or because the memory allocation attempt failed, ** then *pPageSize is set to the old, retained page size before returning. */ int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){ int rc = SQLITE_OK; /* It is not possible to do a full assert_pager_state() here, as this ** function may be called from within PagerOpen(), before the state ** of the Pager object is internally consistent. ** ** At one point this function returned an error if the pager was in ** PAGER_ERROR state. But since PAGER_ERROR state guarantees that ** there is at least one outstanding page reference, this function ** is a no-op for that case anyhow. */ u32 pageSize = *pPageSize; assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) ); if( (pPager->memDb==0 || pPager->dbSize==0) && sqlite3PcacheRefCount(pPager->pPCache)==0 && pageSize && pageSize!=(u32)pPager->pageSize ){ char *pNew = NULL; /* New temp space */ i64 nByte = 0; if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){ rc = sqlite3OsFileSize(pPager->fd, &nByte); } if( rc==SQLITE_OK ){ /* 8 bytes of zeroed overrun space is sufficient so that the b-tree * cell header parser will never run off the end of the allocation */ pNew = (char *)sqlite3PageMalloc(pageSize+8); if( !pNew ){ rc = SQLITE_NOMEM_BKPT; }else{ memset(pNew+pageSize, 0, 8); } } if( rc==SQLITE_OK ){ pager_reset(pPager); rc = sqlite3PcacheSetPageSize(pPager->pPCache, pageSize); } if( rc==SQLITE_OK ){ sqlite3PageFree(pPager->pTmpSpace); pPager->pTmpSpace = pNew; pPager->dbSize = (Pgno)((nByte+pageSize-1)/pageSize); pPager->pageSize = pageSize; }else{ sqlite3PageFree(pNew); } } *pPageSize = pPager->pageSize; if( rc==SQLITE_OK ){ if( nReserve<0 ) nReserve = pPager->nReserve; assert( nReserve>=0 && nReserve<1000 ); pPager->nReserve = (i16)nReserve; pagerFixMaplimit(pPager); } return rc; } /* ** Return a pointer to the "temporary page" buffer held internally ** by the pager. This is a buffer that is big enough to hold the ** entire content of a database page. This buffer is used internally ** during rollback and will be overwritten whenever a rollback ** occurs. But other modules are free to use it too, as long as ** no rollbacks are happening. */ void *sqlite3PagerTempSpace(Pager *pPager){ return pPager->pTmpSpace; } /* ** Attempt to set the maximum database page count if mxPage is positive. ** Make no changes if mxPage is zero or negative. And never reduce the ** maximum page count below the current size of the database. ** ** Regardless of mxPage, return the current maximum page count. */ Pgno sqlite3PagerMaxPageCount(Pager *pPager, Pgno mxPage){ if( mxPage>0 ){ pPager->mxPgno = mxPage; } assert( pPager->eState!=PAGER_OPEN ); /* Called only by OP_MaxPgcnt */ /* assert( pPager->mxPgno>=pPager->dbSize ); */ /* OP_MaxPgcnt ensures that the parameter passed to this function is not ** less than the total number of valid pages in the database. But this ** may be less than Pager.dbSize, and so the assert() above is not valid */ return pPager->mxPgno; } /* ** The following set of routines are used to disable the simulated ** I/O error mechanism. These routines are used to avoid simulated ** errors in places where we do not care about errors. ** ** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops ** and generate no code. */ #ifdef SQLITE_TEST extern int sqlite3_io_error_pending; extern int sqlite3_io_error_hit; static int saved_cnt; void disable_simulated_io_errors(void){ saved_cnt = sqlite3_io_error_pending; sqlite3_io_error_pending = -1; } void enable_simulated_io_errors(void){ sqlite3_io_error_pending = saved_cnt; } #else # define disable_simulated_io_errors() # define enable_simulated_io_errors() #endif /* ** Read the first N bytes from the beginning of the file into memory ** that pDest points to. ** ** If the pager was opened on a transient file (zFilename==""), or ** opened on a file less than N bytes in size, the output buffer is ** zeroed and SQLITE_OK returned. The rationale for this is that this ** function is used to read database headers, and a new transient or ** zero sized database has a header than consists entirely of zeroes. ** ** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered, ** the error code is returned to the caller and the contents of the ** output buffer undefined. */ int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){ int rc = SQLITE_OK; memset(pDest, 0, N); assert( isOpen(pPager->fd) || pPager->tempFile ); /* This routine is only called by btree immediately after creating ** the Pager object. There has not been an opportunity to transition ** to WAL mode yet. */ assert( !pagerUseWal(pPager) ); if( isOpen(pPager->fd) ){ IOTRACE(("DBHDR %p 0 %d\n", pPager, N)) rc = sqlite3OsRead(pPager->fd, pDest, N, 0); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } } return rc; } /* ** This function may only be called when a read-transaction is open on ** the pager. It returns the total number of pages in the database. ** ** However, if the file is between 1 and bytes in size, then ** this is considered a 1 page file. */ void sqlite3PagerPagecount(Pager *pPager, int *pnPage){ assert( pPager->eState>=PAGER_READER ); assert( pPager->eState!=PAGER_WRITER_FINISHED ); *pnPage = (int)pPager->dbSize; } /* ** Try to obtain a lock of type locktype on the database file. If ** a similar or greater lock is already held, this function is a no-op ** (returning SQLITE_OK immediately). ** ** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke ** the busy callback if the lock is currently not available. Repeat ** until the busy callback returns false or until the attempt to ** obtain the lock succeeds. ** ** Return SQLITE_OK on success and an error code if we cannot obtain ** the lock. If the lock is obtained successfully, set the Pager.state ** variable to locktype before returning. */ static int pager_wait_on_lock(Pager *pPager, int locktype){ int rc; /* Return code */ /* Check that this is either a no-op (because the requested lock is ** already held), or one of the transitions that the busy-handler ** may be invoked during, according to the comment above ** sqlite3PagerSetBusyhandler(). */ assert( (pPager->eLock>=locktype) || (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK) || (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK) ); do { rc = pagerLockDb(pPager, locktype); }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) ); return rc; } /* ** Function assertTruncateConstraint(pPager) checks that one of the ** following is true for all dirty pages currently in the page-cache: ** ** a) The page number is less than or equal to the size of the ** current database image, in pages, OR ** ** b) if the page content were written at this time, it would not ** be necessary to write the current content out to the sub-journal ** (as determined by function subjRequiresPage()). ** ** If the condition asserted by this function were not true, and the ** dirty page were to be discarded from the cache via the pagerStress() ** routine, pagerStress() would not write the current page content to ** the database file. If a savepoint transaction were rolled back after ** this happened, the correct behavior would be to restore the current ** content of the page. However, since this content is not present in either ** the database file or the portion of the rollback journal and ** sub-journal rolled back the content could not be restored and the ** database image would become corrupt. It is therefore fortunate that ** this circumstance cannot arise. */ #if defined(SQLITE_DEBUG) static void assertTruncateConstraintCb(PgHdr *pPg){ assert( pPg->flags&PGHDR_DIRTY ); assert( !subjRequiresPage(pPg) || pPg->pgno<=pPg->pPager->dbSize ); } static void assertTruncateConstraint(Pager *pPager){ sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb); } #else # define assertTruncateConstraint(pPager) #endif /* ** Truncate the in-memory database file image to nPage pages. This ** function does not actually modify the database file on disk. It ** just sets the internal state of the pager object so that the ** truncation will be done when the current transaction is committed. ** ** This function is only called right before committing a transaction. ** Once this function has been called, the transaction must either be ** rolled back or committed. It is not safe to call this function and ** then continue writing to the database. */ void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){ assert( pPager->dbSize>=nPage || CORRUPT_DB ); testcase( pPager->dbSizeeState>=PAGER_WRITER_CACHEMOD ); pPager->dbSize = nPage; /* At one point the code here called assertTruncateConstraint() to ** ensure that all pages being truncated away by this operation are, ** if one or more savepoints are open, present in the savepoint ** journal so that they can be restored if the savepoint is rolled ** back. This is no longer necessary as this function is now only ** called right before committing a transaction. So although the ** Pager object may still have open savepoints (Pager.nSavepoint!=0), ** they cannot be rolled back. So the assertTruncateConstraint() call ** is no longer correct. */ } /* ** This function is called before attempting a hot-journal rollback. It ** syncs the journal file to disk, then sets pPager->journalHdr to the ** size of the journal file so that the pager_playback() routine knows ** that the entire journal file has been synced. ** ** Syncing a hot-journal to disk before attempting to roll it back ensures ** that if a power-failure occurs during the rollback, the process that ** attempts rollback following system recovery sees the same journal ** content as this process. ** ** If everything goes as planned, SQLITE_OK is returned. Otherwise, ** an SQLite error code. */ static int pagerSyncHotJournal(Pager *pPager){ int rc = SQLITE_OK; if( !pPager->noSync ){ rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL); } if( rc==SQLITE_OK ){ rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr); } return rc; } #if SQLITE_MAX_MMAP_SIZE>0 /* ** Obtain a reference to a memory mapped page object for page number pgno. ** The new object will use the pointer pData, obtained from xFetch(). ** If successful, set *ppPage to point to the new page reference ** and return SQLITE_OK. Otherwise, return an SQLite error code and set ** *ppPage to zero. ** ** Page references obtained by calling this function should be released ** by calling pagerReleaseMapPage(). */ static int pagerAcquireMapPage( Pager *pPager, /* Pager object */ Pgno pgno, /* Page number */ void *pData, /* xFetch()'d data for this page */ PgHdr **ppPage /* OUT: Acquired page object */ ){ PgHdr *p; /* Memory mapped page to return */ if( pPager->pMmapFreelist ){ *ppPage = p = pPager->pMmapFreelist; pPager->pMmapFreelist = p->pDirty; p->pDirty = 0; assert( pPager->nExtra>=8 ); memset(p->pExtra, 0, 8); }else{ *ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra); if( p==0 ){ sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pData); return SQLITE_NOMEM_BKPT; } p->pExtra = (void *)&p[1]; p->flags = PGHDR_MMAP; p->nRef = 1; p->pPager = pPager; } assert( p->pExtra==(void *)&p[1] ); assert( p->pPage==0 ); assert( p->flags==PGHDR_MMAP ); assert( p->pPager==pPager ); assert( p->nRef==1 ); p->pgno = pgno; p->pData = pData; pPager->nMmapOut++; return SQLITE_OK; } #endif /* ** Release a reference to page pPg. pPg must have been returned by an ** earlier call to pagerAcquireMapPage(). */ static void pagerReleaseMapPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; pPager->nMmapOut--; pPg->pDirty = pPager->pMmapFreelist; pPager->pMmapFreelist = pPg; assert( pPager->fd->pMethods->iVersion>=3 ); sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData); } /* ** Free all PgHdr objects stored in the Pager.pMmapFreelist list. */ static void pagerFreeMapHdrs(Pager *pPager){ PgHdr *p; PgHdr *pNext; for(p=pPager->pMmapFreelist; p; p=pNext){ pNext = p->pDirty; sqlite3_free(p); } } /* Verify that the database file has not be deleted or renamed out from ** under the pager. Return SQLITE_OK if the database is still where it ought ** to be on disk. Return non-zero (SQLITE_READONLY_DBMOVED or some other error ** code from sqlite3OsAccess()) if the database has gone missing. */ static int databaseIsUnmoved(Pager *pPager){ int bHasMoved = 0; int rc; if( pPager->tempFile ) return SQLITE_OK; if( pPager->dbSize==0 ) return SQLITE_OK; assert( pPager->zFilename && pPager->zFilename[0] ); rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_HAS_MOVED, &bHasMoved); if( rc==SQLITE_NOTFOUND ){ /* If the HAS_MOVED file-control is unimplemented, assume that the file ** has not been moved. That is the historical behavior of SQLite: prior to ** version 3.8.3, it never checked */ rc = SQLITE_OK; }else if( rc==SQLITE_OK && bHasMoved ){ rc = SQLITE_READONLY_DBMOVED; } return rc; } /* ** Shutdown the page cache. Free all memory and close all files. ** ** If a transaction was in progress when this routine is called, that ** transaction is rolled back. All outstanding pages are invalidated ** and their memory is freed. Any attempt to use a page associated ** with this page cache after this function returns will likely ** result in a coredump. ** ** This function always succeeds. If a transaction is active an attempt ** is made to roll it back. If an error occurs during the rollback ** a hot journal may be left in the filesystem but no error is returned ** to the caller. */ int sqlite3PagerClose(Pager *pPager, sqlite3 *db){ u8 *pTmp = (u8*)pPager->pTmpSpace; assert( db || pagerUseWal(pPager)==0 ); assert( assert_pager_state(pPager) ); disable_simulated_io_errors(); sqlite3BeginBenignMalloc(); pagerFreeMapHdrs(pPager); /* pPager->errCode = 0; */ pPager->exclusiveMode = 0; #ifndef SQLITE_OMIT_WAL { u8 *a = 0; assert( db || pPager->pWal==0 ); if( db && 0==(db->flags & SQLITE_NoCkptOnClose) && SQLITE_OK==databaseIsUnmoved(pPager) ){ a = pTmp; } sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags, pPager->pageSize,a); pPager->pWal = 0; } #endif pager_reset(pPager); if( MEMDB ){ pager_unlock(pPager); }else{ /* If it is open, sync the journal file before calling UnlockAndRollback. ** If this is not done, then an unsynced portion of the open journal ** file may be played back into the database. If a power failure occurs ** while this is happening, the database could become corrupt. ** ** If an error occurs while trying to sync the journal, shift the pager ** into the ERROR state. This causes UnlockAndRollback to unlock the ** database and close the journal file without attempting to roll it ** back or finalize it. The next database user will have to do hot-journal ** rollback before accessing the database file. */ if( isOpen(pPager->jfd) ){ pager_error(pPager, pagerSyncHotJournal(pPager)); } pagerUnlockAndRollback(pPager); } sqlite3EndBenignMalloc(); enable_simulated_io_errors(); PAGERTRACE(("CLOSE %d\n", PAGERID(pPager))); IOTRACE(("CLOSE %p\n", pPager)) sqlite3OsClose(pPager->jfd); sqlite3OsClose(pPager->fd); sqlite3PageFree(pTmp); sqlite3PcacheClose(pPager->pPCache); assert( !pPager->aSavepoint && !pPager->pInJournal ); assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ); sqlite3_free(pPager); return SQLITE_OK; } #if !defined(NDEBUG) || defined(SQLITE_TEST) /* ** Return the page number for page pPg. */ Pgno sqlite3PagerPagenumber(DbPage *pPg){ return pPg->pgno; } #endif /* ** Increment the reference count for page pPg. */ void sqlite3PagerRef(DbPage *pPg){ sqlite3PcacheRef(pPg); } /* ** Sync the journal. In other words, make sure all the pages that have ** been written to the journal have actually reached the surface of the ** disk and can be restored in the event of a hot-journal rollback. ** ** If the Pager.noSync flag is set, then this function is a no-op. ** Otherwise, the actions required depend on the journal-mode and the ** device characteristics of the file-system, as follows: ** ** * If the journal file is an in-memory journal file, no action need ** be taken. ** ** * Otherwise, if the device does not support the SAFE_APPEND property, ** then the nRec field of the most recently written journal header ** is updated to contain the number of journal records that have ** been written following it. If the pager is operating in full-sync ** mode, then the journal file is synced before this field is updated. ** ** * If the device does not support the SEQUENTIAL property, then ** journal file is synced. ** ** Or, in pseudo-code: ** ** if( NOT ){ ** if( NOT SAFE_APPEND ){ ** if( ) xSync(); ** ** } ** if( NOT SEQUENTIAL ) xSync(); ** } ** ** If successful, this routine clears the PGHDR_NEED_SYNC flag of every ** page currently held in memory before returning SQLITE_OK. If an IO ** error is encountered, then the IO error code is returned to the caller. */ static int syncJournal(Pager *pPager, int newHdr){ int rc; /* Return code */ assert( pPager->eState==PAGER_WRITER_CACHEMOD || pPager->eState==PAGER_WRITER_DBMOD ); assert( assert_pager_state(pPager) ); assert( !pagerUseWal(pPager) ); rc = sqlite3PagerExclusiveLock(pPager); if( rc!=SQLITE_OK ) return rc; if( !pPager->noSync ){ assert( !pPager->tempFile ); if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){ const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd); assert( isOpen(pPager->jfd) ); if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){ /* This block deals with an obscure problem. If the last connection ** that wrote to this database was operating in persistent-journal ** mode, then the journal file may at this point actually be larger ** than Pager.journalOff bytes. If the next thing in the journal ** file happens to be a journal-header (written as part of the ** previous connection's transaction), and a crash or power-failure ** occurs after nRec is updated but before this connection writes ** anything else to the journal file (or commits/rolls back its ** transaction), then SQLite may become confused when doing the ** hot-journal rollback following recovery. It may roll back all ** of this connections data, then proceed to rolling back the old, ** out-of-date data that follows it. Database corruption. ** ** To work around this, if the journal file does appear to contain ** a valid header following Pager.journalOff, then write a 0x00 ** byte to the start of it to prevent it from being recognized. ** ** Variable iNextHdrOffset is set to the offset at which this ** problematic header will occur, if it exists. aMagic is used ** as a temporary buffer to inspect the first couple of bytes of ** the potential journal header. */ i64 iNextHdrOffset; u8 aMagic[8]; u8 zHeader[sizeof(aJournalMagic)+4]; memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic)); put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec); iNextHdrOffset = journalHdrOffset(pPager); rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset); if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){ static const u8 zerobyte = 0; rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset); } if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){ return rc; } /* Write the nRec value into the journal file header. If in ** full-synchronous mode, sync the journal first. This ensures that ** all data has really hit the disk before nRec is updated to mark ** it as a candidate for rollback. ** ** This is not required if the persistent media supports the ** SAFE_APPEND property. Because in this case it is not possible ** for garbage data to be appended to the file, the nRec field ** is populated with 0xFFFFFFFF when the journal header is written ** and never needs to be updated. */ if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager))); IOTRACE(("JSYNC %p\n", pPager)) rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags); if( rc!=SQLITE_OK ) return rc; } IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr)); rc = sqlite3OsWrite( pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr ); if( rc!=SQLITE_OK ) return rc; } if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager))); IOTRACE(("JSYNC %p\n", pPager)) rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags| (pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0) ); if( rc!=SQLITE_OK ) return rc; } pPager->journalHdr = pPager->journalOff; if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){ pPager->nRec = 0; rc = writeJournalHdr(pPager); if( rc!=SQLITE_OK ) return rc; } }else{ pPager->journalHdr = pPager->journalOff; } } /* Unless the pager is in noSync mode, the journal file was just ** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on ** all pages. */ sqlite3PcacheClearSyncFlags(pPager->pPCache); pPager->eState = PAGER_WRITER_DBMOD; assert( assert_pager_state(pPager) ); return SQLITE_OK; } /* ** The argument is the first in a linked list of dirty pages connected ** by the PgHdr.pDirty pointer. This function writes each one of the ** in-memory pages in the list to the database file. The argument may ** be NULL, representing an empty list. In this case this function is ** a no-op. ** ** The pager must hold at least a RESERVED lock when this function ** is called. Before writing anything to the database file, this lock ** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained, ** SQLITE_BUSY is returned and no data is written to the database file. ** ** If the pager is a temp-file pager and the actual file-system file ** is not yet open, it is created and opened before any data is ** written out. ** ** Once the lock has been upgraded and, if necessary, the file opened, ** the pages are written out to the database file in list order. Writing ** a page is skipped if it meets either of the following criteria: ** ** * The page number is greater than Pager.dbSize, or ** * The PGHDR_DONT_WRITE flag is set on the page. ** ** If writing out a page causes the database file to grow, Pager.dbFileSize ** is updated accordingly. If page 1 is written out, then the value cached ** in Pager.dbFileVers[] is updated to match the new value stored in ** the database file. ** ** If everything is successful, SQLITE_OK is returned. If an IO error ** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot ** be obtained, SQLITE_BUSY is returned. */ static int pager_write_pagelist(Pager *pPager, PgHdr *pList){ int rc = SQLITE_OK; /* Return code */ /* This function is only called for rollback pagers in WRITER_DBMOD state. */ assert( !pagerUseWal(pPager) ); assert( pPager->tempFile || pPager->eState==PAGER_WRITER_DBMOD ); assert( pPager->eLock==EXCLUSIVE_LOCK ); assert( isOpen(pPager->fd) || pList->pDirty==0 ); /* If the file is a temp-file has not yet been opened, open it now. It ** is not possible for rc to be other than SQLITE_OK if this branch ** is taken, as pager_wait_on_lock() is a no-op for temp-files. */ if( !isOpen(pPager->fd) ){ assert( pPager->tempFile && rc==SQLITE_OK ); rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags); } /* Before the first write, give the VFS a hint of what the final ** file size will be. */ assert( rc!=SQLITE_OK || isOpen(pPager->fd) ); if( rc==SQLITE_OK && pPager->dbHintSizedbSize && (pList->pDirty || pList->pgno>pPager->dbHintSize) ){ sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize; sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile); pPager->dbHintSize = pPager->dbSize; } while( rc==SQLITE_OK && pList ){ Pgno pgno = pList->pgno; /* If there are dirty pages in the page cache with page numbers greater ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to ** make the file smaller (presumably by auto-vacuum code). Do not write ** any such pages to the file. ** ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag ** set (set by sqlite3PagerDontWrite()). */ if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){ i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */ char *pData; /* Data to write */ assert( (pList->flags&PGHDR_NEED_SYNC)==0 ); if( pList->pgno==1 ) pager_write_changecounter(pList); pData = pList->pData; /* Write out the page data. */ rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset); /* If page 1 was just written, update Pager.dbFileVers to match ** the value now stored in the database file. If writing this ** page caused the database file to grow, update dbFileSize. */ if( pgno==1 ){ memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers)); } if( pgno>pPager->dbFileSize ){ pPager->dbFileSize = pgno; } pPager->aStat[PAGER_STAT_WRITE]++; /* Update any backup objects copying the contents of this pager. */ sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData); PAGERTRACE(("STORE %d page %d hash(%08x)\n", PAGERID(pPager), pgno, pager_pagehash(pList))); IOTRACE(("PGOUT %p %d\n", pPager, pgno)); PAGER_INCR(sqlite3_pager_writedb_count); }else{ PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno)); } pager_set_pagehash(pList); pList = pList->pDirty; } return rc; } /* ** Ensure that the sub-journal file is open. If it is already open, this ** function is a no-op. ** ** SQLITE_OK is returned if everything goes according to plan. An ** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() ** fails. */ static int openSubJournal(Pager *pPager){ int rc = SQLITE_OK; if( !isOpen(pPager->sjfd) ){ const int flags = SQLITE_OPEN_SUBJOURNAL | SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE; int nStmtSpill = sqlite3Config.nStmtSpill; if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){ nStmtSpill = -1; } rc = sqlite3JournalOpen(pPager->pVfs, 0, pPager->sjfd, flags, nStmtSpill); } return rc; } /* ** Append a record of the current state of page pPg to the sub-journal. ** ** If successful, set the bit corresponding to pPg->pgno in the bitvecs ** for all open savepoints before returning. ** ** This function returns SQLITE_OK if everything is successful, an IO ** error code if the attempt to write to the sub-journal fails, or ** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint ** bitvec. */ static int subjournalPage(PgHdr *pPg){ int rc = SQLITE_OK; Pager *pPager = pPg->pPager; if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ /* Open the sub-journal, if it has not already been opened */ assert( pPager->useJournal ); assert( isOpen(pPager->jfd) || pagerUseWal(pPager) ); assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 ); assert( pagerUseWal(pPager) || pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize ); rc = openSubJournal(pPager); /* If the sub-journal was opened successfully (or was already open), ** write the journal record into the file. */ if( rc==SQLITE_OK ){ void *pData = pPg->pData; i64 offset = (i64)pPager->nSubRec*(4+pPager->pageSize); char *pData2; pData2 = pData; PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno)); rc = write32bits(pPager->sjfd, offset, pPg->pgno); if( rc==SQLITE_OK ){ rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4); } } } if( rc==SQLITE_OK ){ pPager->nSubRec++; assert( pPager->nSavepoint>0 ); rc = addToSavepointBitvecs(pPager, pPg->pgno); } return rc; } static int subjournalPageIfRequired(PgHdr *pPg){ if( subjRequiresPage(pPg) ){ return subjournalPage(pPg); }else{ return SQLITE_OK; } } /* ** This function is called by the pcache layer when it has reached some ** soft memory limit. The first argument is a pointer to a Pager object ** (cast as a void*). The pager is always 'purgeable' (not an in-memory ** database). The second argument is a reference to a page that is ** currently dirty but has no outstanding references. The page ** is always associated with the Pager object passed as the first ** argument. ** ** The job of this function is to make pPg clean by writing its contents ** out to the database file, if possible. This may involve syncing the ** journal file. ** ** If successful, sqlite3PcacheMakeClean() is called on the page and ** SQLITE_OK returned. If an IO error occurs while trying to make the ** page clean, the IO error code is returned. If the page cannot be ** made clean for some other reason, but no error occurs, then SQLITE_OK ** is returned by sqlite3PcacheMakeClean() is not called. */ static int pagerStress(void *p, PgHdr *pPg){ Pager *pPager = (Pager *)p; int rc = SQLITE_OK; assert( pPg->pPager==pPager ); assert( pPg->flags&PGHDR_DIRTY ); /* The doNotSpill NOSYNC bit is set during times when doing a sync of ** journal (and adding a new header) is not allowed. This occurs ** during calls to sqlite3PagerWrite() while trying to journal multiple ** pages belonging to the same sector. ** ** The doNotSpill ROLLBACK and OFF bits inhibits all cache spilling ** regardless of whether or not a sync is required. This is set during ** a rollback or by user request, respectively. ** ** Spilling is also prohibited when in an error state since that could ** lead to database corruption. In the current implementation it ** is impossible for sqlite3PcacheFetch() to be called with createFlag==3 ** while in the error state, hence it is impossible for this routine to ** be called in the error state. Nevertheless, we include a NEVER() ** test for the error state as a safeguard against future changes. */ if( NEVER(pPager->errCode) ) return SQLITE_OK; testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK ); testcase( pPager->doNotSpill & SPILLFLAG_OFF ); testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC ); if( pPager->doNotSpill && ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0 || (pPg->flags & PGHDR_NEED_SYNC)!=0) ){ return SQLITE_OK; } pPager->aStat[PAGER_STAT_SPILL]++; pPg->pDirty = 0; if( pagerUseWal(pPager) ){ /* Write a single frame for this page to the log. */ rc = subjournalPageIfRequired(pPg); if( rc==SQLITE_OK ){ rc = pagerWalFrames(pPager, pPg, 0, 0); } }else{ #ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE if( pPager->tempFile==0 ){ rc = sqlite3JournalCreate(pPager->jfd); if( rc!=SQLITE_OK ) return pager_error(pPager, rc); } #endif /* Sync the journal file if required. */ if( pPg->flags&PGHDR_NEED_SYNC || pPager->eState==PAGER_WRITER_CACHEMOD ){ rc = syncJournal(pPager, 1); } /* Write the contents of the page out to the database file. */ if( rc==SQLITE_OK ){ assert( (pPg->flags&PGHDR_NEED_SYNC)==0 ); rc = pager_write_pagelist(pPager, pPg); } } /* Mark the page as clean. */ if( rc==SQLITE_OK ){ PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno)); sqlite3PcacheMakeClean(pPg); } return pager_error(pPager, rc); } /* ** Flush all unreferenced dirty pages to disk. */ int sqlite3PagerFlush(Pager *pPager){ int rc = pPager->errCode; if( !MEMDB ){ PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache); assert( assert_pager_state(pPager) ); while( rc==SQLITE_OK && pList ){ PgHdr *pNext = pList->pDirty; if( pList->nRef==0 ){ rc = pagerStress((void*)pPager, pList); } pList = pNext; } } return rc; } /* ** Allocate and initialize a new Pager object and put a pointer to it ** in *ppPager. The pager should eventually be freed by passing it ** to sqlite3PagerClose(). ** ** The zFilename argument is the path to the database file to open. ** If zFilename is NULL then a randomly-named temporary file is created ** and used as the file to be cached. Temporary files are be deleted ** automatically when they are closed. If zFilename is ":memory:" then ** all information is held in cache. It is never written to disk. ** This can be used to implement an in-memory database. ** ** The nExtra parameter specifies the number of bytes of space allocated ** along with each page reference. This space is available to the user ** via the sqlite3PagerGetExtra() API. When a new page is allocated, the ** first 8 bytes of this space are zeroed but the remainder is uninitialized. ** (The extra space is used by btree as the MemPage object.) ** ** The flags argument is used to specify properties that affect the ** operation of the pager. It should be passed some bitwise combination ** of the PAGER_* flags. ** ** The vfsFlags parameter is a bitmask to pass to the flags parameter ** of the xOpen() method of the supplied VFS when opening files. ** ** If the pager object is allocated and the specified file opened ** successfully, SQLITE_OK is returned and *ppPager set to point to ** the new pager object. If an error occurs, *ppPager is set to NULL ** and error code returned. This function may return SQLITE_NOMEM ** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or ** various SQLITE_IO_XXX errors. */ int sqlite3PagerOpen( sqlite3_vfs *pVfs, /* The virtual file system to use */ Pager **ppPager, /* OUT: Return the Pager structure here */ const char *zFilename, /* Name of the database file to open */ int nExtra, /* Extra bytes append to each in-memory page */ int flags, /* flags controlling this file */ int vfsFlags, /* flags passed through to sqlite3_vfs.xOpen() */ void (*xReinit)(DbPage*) /* Function to reinitialize pages */ ){ u8 *pPtr; Pager *pPager = 0; /* Pager object to allocate and return */ int rc = SQLITE_OK; /* Return code */ int tempFile = 0; /* True for temp files (incl. in-memory files) */ int memDb = 0; /* True if this is an in-memory file */ #ifndef SQLITE_OMIT_DESERIALIZE int memJM = 0; /* Memory journal mode */ #else # define memJM 0 #endif int readOnly = 0; /* True if this is a read-only file */ int journalFileSize; /* Bytes to allocate for each journal fd */ char *zPathname = 0; /* Full path to database file */ int nPathname = 0; /* Number of bytes in zPathname */ int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */ int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */ u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */ const char *zUri = 0; /* URI args to copy */ int nUriByte = 1; /* Number of bytes of URI args at *zUri */ int nUri = 0; /* Number of URI parameters */ /* Figure out how much space is required for each journal file-handle ** (there are two of them, the main journal and the sub-journal). */ journalFileSize = ROUND8(sqlite3JournalSize(pVfs)); /* Set the output variable to NULL in case an error occurs. */ *ppPager = 0; #ifndef SQLITE_OMIT_MEMORYDB if( flags & PAGER_MEMORY ){ memDb = 1; if( zFilename && zFilename[0] ){ zPathname = sqlite3DbStrDup(0, zFilename); if( zPathname==0 ) return SQLITE_NOMEM_BKPT; nPathname = sqlite3Strlen30(zPathname); zFilename = 0; } } #endif /* Compute and store the full pathname in an allocated buffer pointed ** to by zPathname, length nPathname. Or, if this is a temporary file, ** leave both nPathname and zPathname set to 0. */ if( zFilename && zFilename[0] ){ const char *z; nPathname = pVfs->mxPathname+1; zPathname = sqlite3DbMallocRaw(0, nPathname*2); if( zPathname==0 ){ return SQLITE_NOMEM_BKPT; } zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */ rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname); if( rc!=SQLITE_OK ){ if( rc==SQLITE_OK_SYMLINK ){ if( vfsFlags & SQLITE_OPEN_NOFOLLOW ){ rc = SQLITE_CANTOPEN_SYMLINK; }else{ rc = SQLITE_OK; } } } nPathname = sqlite3Strlen30(zPathname); z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1]; while( *z ){ z += strlen(z)+1; z += strlen(z)+1; nUri++; } nUriByte = (int)(&z[1] - zUri); assert( nUriByte>=1 ); if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){ /* This branch is taken when the journal path required by ** the database being opened will be more than pVfs->mxPathname ** bytes in length. This means the database cannot be opened, ** as it will not be possible to open the journal file or even ** check for a hot-journal before reading. */ rc = SQLITE_CANTOPEN_BKPT; } if( rc!=SQLITE_OK ){ sqlite3DbFree(0, zPathname); return rc; } } /* Allocate memory for the Pager structure, PCache object, the ** three file descriptors, the database file name and the journal ** file name. The layout in memory is as follows: ** ** Pager object (sizeof(Pager) bytes) ** PCache object (sqlite3PcacheSize() bytes) ** Database file handle (pVfs->szOsFile bytes) ** Sub-journal file handle (journalFileSize bytes) ** Main journal file handle (journalFileSize bytes) ** Ptr back to the Pager (sizeof(Pager*) bytes) ** \0\0\0\0 database prefix (4 bytes) ** Database file name (nPathname+1 bytes) ** URI query parameters (nUriByte bytes) ** Journal filename (nPathname+8+1 bytes) ** WAL filename (nPathname+4+1 bytes) ** \0\0\0 terminator (3 bytes) ** ** Some 3rd-party software, over which we have no control, depends on ** the specific order of the filenames and the \0 separators between them ** so that it can (for example) find the database filename given the WAL ** filename without using the sqlite3_filename_database() API. This is a ** misuse of SQLite and a bug in the 3rd-party software, but the 3rd-party ** software is in widespread use, so we try to avoid changing the filename ** order and formatting if possible. In particular, the details of the ** filename format expected by 3rd-party software should be as follows: ** ** - Main Database Path ** - \0 ** - Multiple URI components consisting of: ** - Key ** - \0 ** - Value ** - \0 ** - \0 ** - Journal Path ** - \0 ** - WAL Path (zWALName) ** - \0 ** ** The sqlite3_create_filename() interface and the databaseFilename() utility ** that is used by sqlite3_filename_database() and kin also depend on the ** specific formatting and order of the various filenames, so if the format ** changes here, be sure to change it there as well. */ pPtr = (u8 *)sqlite3MallocZero( ROUND8(sizeof(*pPager)) + /* Pager structure */ ROUND8(pcacheSize) + /* PCache object */ ROUND8(pVfs->szOsFile) + /* The main db file */ journalFileSize * 2 + /* The two journal files */ sizeof(pPager) + /* Space to hold a pointer */ 4 + /* Database prefix */ nPathname + 1 + /* database filename */ nUriByte + /* query parameters */ nPathname + 8 + 1 + /* Journal filename */ #ifndef SQLITE_OMIT_WAL nPathname + 4 + 1 + /* WAL filename */ #endif 3 /* Terminator */ ); assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) ); if( !pPtr ){ sqlite3DbFree(0, zPathname); return SQLITE_NOMEM_BKPT; } pPager = (Pager*)pPtr; pPtr += ROUND8(sizeof(*pPager)); pPager->pPCache = (PCache*)pPtr; pPtr += ROUND8(pcacheSize); pPager->fd = (sqlite3_file*)pPtr; pPtr += ROUND8(pVfs->szOsFile); pPager->sjfd = (sqlite3_file*)pPtr; pPtr += journalFileSize; pPager->jfd = (sqlite3_file*)pPtr; pPtr += journalFileSize; assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) ); memcpy(pPtr, &pPager, sizeof(pPager)); pPtr += sizeof(pPager); /* Fill in the Pager.zFilename and pPager.zQueryParam fields */ pPtr += 4; /* Skip zero prefix */ pPager->zFilename = (char*)pPtr; if( nPathname>0 ){ memcpy(pPtr, zPathname, nPathname); pPtr += nPathname + 1; if( zUri ){ memcpy(pPtr, zUri, nUriByte); pPtr += nUriByte; }else{ pPtr++; } } /* Fill in Pager.zJournal */ if( nPathname>0 ){ pPager->zJournal = (char*)pPtr; memcpy(pPtr, zPathname, nPathname); pPtr += nPathname; memcpy(pPtr, "-journal",8); pPtr += 8 + 1; #ifdef SQLITE_ENABLE_8_3_NAMES sqlite3FileSuffix3(zFilename,pPager->zJournal); pPtr = (u8*)(pPager->zJournal + sqlite3Strlen30(pPager->zJournal)+1); #endif }else{ pPager->zJournal = 0; } #ifndef SQLITE_OMIT_WAL /* Fill in Pager.zWal */ if( nPathname>0 ){ pPager->zWal = (char*)pPtr; memcpy(pPtr, zPathname, nPathname); pPtr += nPathname; memcpy(pPtr, "-wal", 4); pPtr += 4 + 1; #ifdef SQLITE_ENABLE_8_3_NAMES sqlite3FileSuffix3(zFilename, pPager->zWal); pPtr = (u8*)(pPager->zWal + sqlite3Strlen30(pPager->zWal)+1); #endif }else{ pPager->zWal = 0; } #endif (void)pPtr; /* Suppress warning about unused pPtr value */ if( nPathname ) sqlite3DbFree(0, zPathname); pPager->pVfs = pVfs; pPager->vfsFlags = vfsFlags; /* Open the pager file. */ if( zFilename && zFilename[0] ){ int fout = 0; /* VFS flags returned by xOpen() */ rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout); assert( !memDb ); #ifndef SQLITE_OMIT_DESERIALIZE pPager->memVfs = memJM = (fout&SQLITE_OPEN_MEMORY)!=0; #endif readOnly = (fout&SQLITE_OPEN_READONLY)!=0; /* If the file was successfully opened for read/write access, ** choose a default page size in case we have to create the ** database file. The default page size is the maximum of: ** ** + SQLITE_DEFAULT_PAGE_SIZE, ** + The value returned by sqlite3OsSectorSize() ** + The largest page size that can be written atomically. */ if( rc==SQLITE_OK ){ int iDc = sqlite3OsDeviceCharacteristics(pPager->fd); if( !readOnly ){ setSectorSize(pPager); assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE); if( szPageDfltsectorSize ){ if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){ szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE; }else{ szPageDflt = (u32)pPager->sectorSize; } } #ifdef SQLITE_ENABLE_ATOMIC_WRITE { int ii; assert(SQLITE_IOCAP_ATOMIC512==(512>>8)); assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8)); assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536); for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){ if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){ szPageDflt = ii; } } } #endif } pPager->noLock = sqlite3_uri_boolean(pPager->zFilename, "nolock", 0); if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0 || sqlite3_uri_boolean(pPager->zFilename, "immutable", 0) ){ vfsFlags |= SQLITE_OPEN_READONLY; goto act_like_temp_file; } } }else{ /* If a temporary file is requested, it is not opened immediately. ** In this case we accept the default page size and delay actually ** opening the file until the first call to OsWrite(). ** ** This branch is also run for an in-memory database. An in-memory ** database is the same as a temp-file that is never written out to ** disk and uses an in-memory rollback journal. ** ** This branch also runs for files marked as immutable. */ act_like_temp_file: tempFile = 1; pPager->eState = PAGER_READER; /* Pretend we already have a lock */ pPager->eLock = EXCLUSIVE_LOCK; /* Pretend we are in EXCLUSIVE mode */ pPager->noLock = 1; /* Do no locking */ readOnly = (vfsFlags&SQLITE_OPEN_READONLY); } /* The following call to PagerSetPagesize() serves to set the value of ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer. */ if( rc==SQLITE_OK ){ assert( pPager->memDb==0 ); rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1); testcase( rc!=SQLITE_OK ); } /* Initialize the PCache object. */ if( rc==SQLITE_OK ){ nExtra = ROUND8(nExtra); assert( nExtra>=8 && nExtra<1000 ); rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb, !memDb?pagerStress:0, (void *)pPager, pPager->pPCache); } /* If an error occurred above, free the Pager structure and close the file. */ if( rc!=SQLITE_OK ){ sqlite3OsClose(pPager->fd); sqlite3PageFree(pPager->pTmpSpace); sqlite3_free(pPager); return rc; } PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename)); IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename)) pPager->useJournal = (u8)useJournal; /* pPager->stmtOpen = 0; */ /* pPager->stmtInUse = 0; */ /* pPager->nRef = 0; */ /* pPager->stmtSize = 0; */ /* pPager->stmtJSize = 0; */ /* pPager->nPage = 0; */ pPager->mxPgno = SQLITE_MAX_PAGE_COUNT; /* pPager->state = PAGER_UNLOCK; */ /* pPager->errMask = 0; */ pPager->tempFile = (u8)tempFile; assert( tempFile==PAGER_LOCKINGMODE_NORMAL || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE ); assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 ); pPager->exclusiveMode = (u8)tempFile; pPager->changeCountDone = pPager->tempFile; pPager->memDb = (u8)memDb; pPager->readOnly = (u8)readOnly; assert( useJournal || pPager->tempFile ); pPager->noSync = pPager->tempFile; if( pPager->noSync ){ assert( pPager->fullSync==0 ); assert( pPager->extraSync==0 ); assert( pPager->syncFlags==0 ); assert( pPager->walSyncFlags==0 ); }else{ pPager->fullSync = 1; pPager->extraSync = 0; pPager->syncFlags = SQLITE_SYNC_NORMAL; pPager->walSyncFlags = SQLITE_SYNC_NORMAL | (SQLITE_SYNC_NORMAL<<2); } /* pPager->pFirst = 0; */ /* pPager->pFirstSynced = 0; */ /* pPager->pLast = 0; */ pPager->nExtra = (u16)nExtra; pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT; assert( isOpen(pPager->fd) || tempFile ); setSectorSize(pPager); if( !useJournal ){ pPager->journalMode = PAGER_JOURNALMODE_OFF; }else if( memDb || memJM ){ pPager->journalMode = PAGER_JOURNALMODE_MEMORY; } /* pPager->xBusyHandler = 0; */ /* pPager->pBusyHandlerArg = 0; */ pPager->xReiniter = xReinit; setGetterMethod(pPager); /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */ /* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */ *ppPager = pPager; return SQLITE_OK; } /* ** Return the sqlite3_file for the main database given the name ** of the corresonding WAL or Journal name as passed into ** xOpen. */ sqlite3_file *sqlite3_database_file_object(const char *zName){ Pager *pPager; while( zName[-1]!=0 || zName[-2]!=0 || zName[-3]!=0 || zName[-4]!=0 ){ zName--; } pPager = *(Pager**)(zName - 4 - sizeof(Pager*)); return pPager->fd; } /* ** This function is called after transitioning from PAGER_UNLOCK to ** PAGER_SHARED state. It tests if there is a hot journal present in ** the file-system for the given pager. A hot journal is one that ** needs to be played back. According to this function, a hot-journal ** file exists if the following criteria are met: ** ** * The journal file exists in the file system, and ** * No process holds a RESERVED or greater lock on the database file, and ** * The database file itself is greater than 0 bytes in size, and ** * The first byte of the journal file exists and is not 0x00. ** ** If the current size of the database file is 0 but a journal file ** exists, that is probably an old journal left over from a prior ** database with the same name. In this case the journal file is ** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK ** is returned. ** ** This routine does not check if there is a super-journal filename ** at the end of the file. If there is, and that super-journal file ** does not exist, then the journal file is not really hot. In this ** case this routine will return a false-positive. The pager_playback() ** routine will discover that the journal file is not really hot and ** will not roll it back. ** ** If a hot-journal file is found to exist, *pExists is set to 1 and ** SQLITE_OK returned. If no hot-journal file is present, *pExists is ** set to 0 and SQLITE_OK returned. If an IO error occurs while trying ** to determine whether or not a hot-journal file exists, the IO error ** code is returned and the value of *pExists is undefined. */ static int hasHotJournal(Pager *pPager, int *pExists){ sqlite3_vfs * const pVfs = pPager->pVfs; int rc = SQLITE_OK; /* Return code */ int exists = 1; /* True if a journal file is present */ int jrnlOpen = !!isOpen(pPager->jfd); assert( pPager->useJournal ); assert( isOpen(pPager->fd) ); assert( pPager->eState==PAGER_OPEN ); assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN )); *pExists = 0; if( !jrnlOpen ){ rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists); } if( rc==SQLITE_OK && exists ){ int locked = 0; /* True if some process holds a RESERVED lock */ /* Race condition here: Another process might have been holding the ** the RESERVED lock and have a journal open at the sqlite3OsAccess() ** call above, but then delete the journal and drop the lock before ** we get to the following sqlite3OsCheckReservedLock() call. If that ** is the case, this routine might think there is a hot journal when ** in fact there is none. This results in a false-positive which will ** be dealt with by the playback routine. Ticket #3883. */ rc = sqlite3OsCheckReservedLock(pPager->fd, &locked); if( rc==SQLITE_OK && !locked ){ Pgno nPage; /* Number of pages in database file */ assert( pPager->tempFile==0 ); rc = pagerPagecount(pPager, &nPage); if( rc==SQLITE_OK ){ /* If the database is zero pages in size, that means that either (1) the ** journal is a remnant from a prior database with the same name where ** the database file but not the journal was deleted, or (2) the initial ** transaction that populates a new database is being rolled back. ** In either case, the journal file can be deleted. However, take care ** not to delete the journal file if it is already open due to ** journal_mode=PERSIST. */ if( nPage==0 && !jrnlOpen ){ sqlite3BeginBenignMalloc(); if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){ sqlite3OsDelete(pVfs, pPager->zJournal, 0); if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK); } sqlite3EndBenignMalloc(); }else{ /* The journal file exists and no other connection has a reserved ** or greater lock on the database file. Now check that there is ** at least one non-zero bytes at the start of the journal file. ** If there is, then we consider this journal to be hot. If not, ** it can be ignored. */ if( !jrnlOpen ){ int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL; rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f); } if( rc==SQLITE_OK ){ u8 first = 0; rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } if( !jrnlOpen ){ sqlite3OsClose(pPager->jfd); } *pExists = (first!=0); }else if( rc==SQLITE_CANTOPEN ){ /* If we cannot open the rollback journal file in order to see if ** it has a zero header, that might be due to an I/O error, or ** it might be due to the race condition described above and in ** ticket #3883. Either way, assume that the journal is hot. ** This might be a false positive. But if it is, then the ** automatic journal playback and recovery mechanism will deal ** with it under an EXCLUSIVE lock where we do not need to ** worry so much with race conditions. */ *pExists = 1; rc = SQLITE_OK; } } } } } return rc; } /* ** This function is called to obtain a shared lock on the database file. ** It is illegal to call sqlite3PagerGet() until after this function ** has been successfully called. If a shared-lock is already held when ** this function is called, it is a no-op. ** ** The following operations are also performed by this function. ** ** 1) If the pager is currently in PAGER_OPEN state (no lock held ** on the database file), then an attempt is made to obtain a ** SHARED lock on the database file. Immediately after obtaining ** the SHARED lock, the file-system is checked for a hot-journal, ** which is played back if present. Following any hot-journal ** rollback, the contents of the cache are validated by checking ** the 'change-counter' field of the database file header and ** discarded if they are found to be invalid. ** ** 2) If the pager is running in exclusive-mode, and there are currently ** no outstanding references to any pages, and is in the error state, ** then an attempt is made to clear the error state by discarding ** the contents of the page cache and rolling back any open journal ** file. ** ** If everything is successful, SQLITE_OK is returned. If an IO error ** occurs while locking the database, checking for a hot-journal file or ** rolling back a journal file, the IO error code is returned. */ int sqlite3PagerSharedLock(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ /* This routine is only called from b-tree and only when there are no ** outstanding pages. This implies that the pager state should either ** be OPEN or READER. READER is only possible if the pager is or was in ** exclusive access mode. */ assert( sqlite3PcacheRefCount(pPager->pPCache)==0 ); assert( assert_pager_state(pPager) ); assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER ); assert( pPager->errCode==SQLITE_OK ); if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){ int bHotJournal = 1; /* True if there exists a hot journal-file */ assert( !MEMDB ); assert( pPager->tempFile==0 || pPager->eLock==EXCLUSIVE_LOCK ); rc = pager_wait_on_lock(pPager, SHARED_LOCK); if( rc!=SQLITE_OK ){ assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK ); goto failed; } /* If a journal file exists, and there is no RESERVED lock on the ** database file, then it either needs to be played back or deleted. */ if( pPager->eLock<=SHARED_LOCK ){ rc = hasHotJournal(pPager, &bHotJournal); } if( rc!=SQLITE_OK ){ goto failed; } if( bHotJournal ){ if( pPager->readOnly ){ rc = SQLITE_READONLY_ROLLBACK; goto failed; } /* Get an EXCLUSIVE lock on the database file. At this point it is ** important that a RESERVED lock is not obtained on the way to the ** EXCLUSIVE lock. If it were, another process might open the ** database file, detect the RESERVED lock, and conclude that the ** database is safe to read while this process is still rolling the ** hot-journal back. ** ** Because the intermediate RESERVED lock is not requested, any ** other process attempting to access the database file will get to ** this point in the code and fail to obtain its own EXCLUSIVE lock ** on the database file. ** ** Unless the pager is in locking_mode=exclusive mode, the lock is ** downgraded to SHARED_LOCK before this function returns. */ rc = pagerLockDb(pPager, EXCLUSIVE_LOCK); if( rc!=SQLITE_OK ){ goto failed; } /* If it is not already open and the file exists on disk, open the ** journal for read/write access. Write access is required because ** in exclusive-access mode the file descriptor will be kept open ** and possibly used for a transaction later on. Also, write-access ** is usually required to finalize the journal in journal_mode=persist ** mode (and also for journal_mode=truncate on some systems). ** ** If the journal does not exist, it usually means that some ** other connection managed to get in and roll it back before ** this connection obtained the exclusive lock above. Or, it ** may mean that the pager was in the error-state when this ** function was called and the journal file does not exist. */ if( !isOpen(pPager->jfd) ){ sqlite3_vfs * const pVfs = pPager->pVfs; int bExists; /* True if journal file exists */ rc = sqlite3OsAccess( pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists); if( rc==SQLITE_OK && bExists ){ int fout = 0; int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL; assert( !pPager->tempFile ); rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout); assert( rc!=SQLITE_OK || isOpen(pPager->jfd) ); if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){ rc = SQLITE_CANTOPEN_BKPT; sqlite3OsClose(pPager->jfd); } } } /* Playback and delete the journal. Drop the database write ** lock and reacquire the read lock. Purge the cache before ** playing back the hot-journal so that we don't end up with ** an inconsistent cache. Sync the hot journal before playing ** it back since the process that crashed and left the hot journal ** probably did not sync it and we are required to always sync ** the journal before playing it back. */ if( isOpen(pPager->jfd) ){ assert( rc==SQLITE_OK ); rc = pagerSyncHotJournal(pPager); if( rc==SQLITE_OK ){ rc = pager_playback(pPager, !pPager->tempFile); pPager->eState = PAGER_OPEN; } }else if( !pPager->exclusiveMode ){ pagerUnlockDb(pPager, SHARED_LOCK); } if( rc!=SQLITE_OK ){ /* This branch is taken if an error occurs while trying to open ** or roll back a hot-journal while holding an EXCLUSIVE lock. The ** pager_unlock() routine will be called before returning to unlock ** the file. If the unlock attempt fails, then Pager.eLock must be ** set to UNKNOWN_LOCK (see the comment above the #define for ** UNKNOWN_LOCK above for an explanation). ** ** In order to get pager_unlock() to do this, set Pager.eState to ** PAGER_ERROR now. This is not actually counted as a transition ** to ERROR state in the state diagram at the top of this file, ** since we know that the same call to pager_unlock() will very ** shortly transition the pager object to the OPEN state. Calling ** assert_pager_state() would fail now, as it should not be possible ** to be in ERROR state when there are zero outstanding page ** references. */ pager_error(pPager, rc); goto failed; } assert( pPager->eState==PAGER_OPEN ); assert( (pPager->eLock==SHARED_LOCK) || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK) ); } if( !pPager->tempFile && pPager->hasHeldSharedLock ){ /* The shared-lock has just been acquired then check to ** see if the database has been modified. If the database has changed, ** flush the cache. The hasHeldSharedLock flag prevents this from ** occurring on the very first access to a file, in order to save a ** single unnecessary sqlite3OsRead() call at the start-up. ** ** Database changes are detected by looking at 15 bytes beginning ** at offset 24 into the file. The first 4 of these 16 bytes are ** a 32-bit counter that is incremented with each change. The ** other bytes change randomly with each file change when ** a codec is in use. ** ** There is a vanishingly small chance that a change will not be ** detected. The chance of an undetected change is so small that ** it can be neglected. */ char dbFileVers[sizeof(pPager->dbFileVers)]; IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers))); rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24); if( rc!=SQLITE_OK ){ if( rc!=SQLITE_IOERR_SHORT_READ ){ goto failed; } memset(dbFileVers, 0, sizeof(dbFileVers)); } if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){ pager_reset(pPager); /* Unmap the database file. It is possible that external processes ** may have truncated the database file and then extended it back ** to its original size while this process was not holding a lock. ** In this case there may exist a Pager.pMap mapping that appears ** to be the right size but is not actually valid. Avoid this ** possibility by unmapping the db here. */ if( USEFETCH(pPager) ){ sqlite3OsUnfetch(pPager->fd, 0, 0); } } } /* If there is a WAL file in the file-system, open this database in WAL ** mode. Otherwise, the following function call is a no-op. */ rc = pagerOpenWalIfPresent(pPager); #ifndef SQLITE_OMIT_WAL assert( pPager->pWal==0 || rc==SQLITE_OK ); #endif } if( pagerUseWal(pPager) ){ assert( rc==SQLITE_OK ); rc = pagerBeginReadTransaction(pPager); } if( pPager->tempFile==0 && pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){ rc = pagerPagecount(pPager, &pPager->dbSize); } failed: if( rc!=SQLITE_OK ){ assert( !MEMDB ); pager_unlock(pPager); assert( pPager->eState==PAGER_OPEN ); }else{ pPager->eState = PAGER_READER; pPager->hasHeldSharedLock = 1; } return rc; } /* ** If the reference count has reached zero, rollback any active ** transaction and unlock the pager. ** ** Except, in locking_mode=EXCLUSIVE when there is nothing to in ** the rollback journal, the unlock is not performed and there is ** nothing to rollback, so this routine is a no-op. */ static void pagerUnlockIfUnused(Pager *pPager){ if( sqlite3PcacheRefCount(pPager->pPCache)==0 ){ assert( pPager->nMmapOut==0 ); /* because page1 is never memory mapped */ pagerUnlockAndRollback(pPager); } } /* ** The page getter methods each try to acquire a reference to a ** page with page number pgno. If the requested reference is ** successfully obtained, it is copied to *ppPage and SQLITE_OK returned. ** ** There are different implementations of the getter method depending ** on the current state of the pager. ** ** getPageNormal() -- The normal getter ** getPageError() -- Used if the pager is in an error state ** getPageMmap() -- Used if memory-mapped I/O is enabled ** ** If the requested page is already in the cache, it is returned. ** Otherwise, a new page object is allocated and populated with data ** read from the database file. In some cases, the pcache module may ** choose not to allocate a new page object and may reuse an existing ** object with no outstanding references. ** ** The extra data appended to a page is always initialized to zeros the ** first time a page is loaded into memory. If the page requested is ** already in the cache when this function is called, then the extra ** data is left as it was when the page object was last used. ** ** If the database image is smaller than the requested page or if ** the flags parameter contains the PAGER_GET_NOCONTENT bit and the ** requested page is not already stored in the cache, then no ** actual disk read occurs. In this case the memory image of the ** page is initialized to all zeros. ** ** If PAGER_GET_NOCONTENT is true, it means that we do not care about ** the contents of the page. This occurs in two scenarios: ** ** a) When reading a free-list leaf page from the database, and ** ** b) When a savepoint is being rolled back and we need to load ** a new page into the cache to be filled with the data read ** from the savepoint journal. ** ** If PAGER_GET_NOCONTENT is true, then the data returned is zeroed instead ** of being read from the database. Additionally, the bits corresponding ** to pgno in Pager.pInJournal (bitvec of pages already written to the ** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open ** savepoints are set. This means if the page is made writable at any ** point in the future, using a call to sqlite3PagerWrite(), its contents ** will not be journaled. This saves IO. ** ** The acquisition might fail for several reasons. In all cases, ** an appropriate error code is returned and *ppPage is set to NULL. ** ** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt ** to find a page in the in-memory cache first. If the page is not already ** in memory, this routine goes to disk to read it in whereas Lookup() ** just returns 0. This routine acquires a read-lock the first time it ** has to go to disk, and could also playback an old journal if necessary. ** Since Lookup() never goes to disk, it never has to deal with locks ** or journal files. */ static int getPageNormal( Pager *pPager, /* The pager open on the database file */ Pgno pgno, /* Page number to fetch */ DbPage **ppPage, /* Write a pointer to the page here */ int flags /* PAGER_GET_XXX flags */ ){ int rc = SQLITE_OK; PgHdr *pPg; u8 noContent; /* True if PAGER_GET_NOCONTENT is set */ sqlite3_pcache_page *pBase; assert( pPager->errCode==SQLITE_OK ); assert( pPager->eState>=PAGER_READER ); assert( assert_pager_state(pPager) ); assert( pPager->hasHeldSharedLock==1 ); if( pgno==0 ) return SQLITE_CORRUPT_BKPT; pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3); if( pBase==0 ){ pPg = 0; rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase); if( rc!=SQLITE_OK ) goto pager_acquire_err; if( pBase==0 ){ rc = SQLITE_NOMEM_BKPT; goto pager_acquire_err; } } pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase); assert( pPg==(*ppPage) ); assert( pPg->pgno==pgno ); assert( pPg->pPager==pPager || pPg->pPager==0 ); noContent = (flags & PAGER_GET_NOCONTENT)!=0; if( pPg->pPager && !noContent ){ /* In this case the pcache already contains an initialized copy of ** the page. Return without further ado. */ assert( pgno!=PAGER_MJ_PGNO(pPager) ); pPager->aStat[PAGER_STAT_HIT]++; return SQLITE_OK; }else{ /* The pager cache has created a new page. Its content needs to ** be initialized. But first some error checks: ** ** (*) obsolete. Was: maximum page number is 2^31 ** (2) Never try to fetch the locking page */ if( pgno==PAGER_MJ_PGNO(pPager) ){ rc = SQLITE_CORRUPT_BKPT; goto pager_acquire_err; } pPg->pPager = pPager; assert( !isOpen(pPager->fd) || !MEMDB ); if( !isOpen(pPager->fd) || pPager->dbSizepPager->mxPgno ){ rc = SQLITE_FULL; goto pager_acquire_err; } if( noContent ){ /* Failure to set the bits in the InJournal bit-vectors is benign. ** It merely means that we might do some extra work to journal a ** page that does not need to be journaled. Nevertheless, be sure ** to test the case where a malloc error occurs while trying to set ** a bit in a bit vector. */ sqlite3BeginBenignMalloc(); if( pgno<=pPager->dbOrigSize ){ TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno); testcase( rc==SQLITE_NOMEM ); } TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno); testcase( rc==SQLITE_NOMEM ); sqlite3EndBenignMalloc(); } memset(pPg->pData, 0, pPager->pageSize); IOTRACE(("ZERO %p %d\n", pPager, pgno)); }else{ assert( pPg->pPager==pPager ); pPager->aStat[PAGER_STAT_MISS]++; rc = readDbPage(pPg); if( rc!=SQLITE_OK ){ goto pager_acquire_err; } } pager_set_pagehash(pPg); } return SQLITE_OK; pager_acquire_err: assert( rc!=SQLITE_OK ); if( pPg ){ sqlite3PcacheDrop(pPg); } pagerUnlockIfUnused(pPager); *ppPage = 0; return rc; } #if SQLITE_MAX_MMAP_SIZE>0 /* The page getter for when memory-mapped I/O is enabled */ static int getPageMMap( Pager *pPager, /* The pager open on the database file */ Pgno pgno, /* Page number to fetch */ DbPage **ppPage, /* Write a pointer to the page here */ int flags /* PAGER_GET_XXX flags */ ){ int rc = SQLITE_OK; PgHdr *pPg = 0; u32 iFrame = 0; /* Frame to read from WAL file */ /* It is acceptable to use a read-only (mmap) page for any page except ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY ** flag was specified by the caller. And so long as the db is not a ** temporary or in-memory database. */ const int bMmapOk = (pgno>1 && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY)) ); assert( USEFETCH(pPager) ); /* Optimization note: Adding the "pgno<=1" term before "pgno==0" here ** allows the compiler optimizer to reuse the results of the "pgno>1" ** test in the previous statement, and avoid testing pgno==0 in the ** common case where pgno is large. */ if( pgno<=1 && pgno==0 ){ return SQLITE_CORRUPT_BKPT; } assert( pPager->eState>=PAGER_READER ); assert( assert_pager_state(pPager) ); assert( pPager->hasHeldSharedLock==1 ); assert( pPager->errCode==SQLITE_OK ); if( bMmapOk && pagerUseWal(pPager) ){ rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame); if( rc!=SQLITE_OK ){ *ppPage = 0; return rc; } } if( bMmapOk && iFrame==0 ){ void *pData = 0; rc = sqlite3OsFetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData ); if( rc==SQLITE_OK && pData ){ if( pPager->eState>PAGER_READER || pPager->tempFile ){ pPg = sqlite3PagerLookup(pPager, pgno); } if( pPg==0 ){ rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg); }else{ sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData); } if( pPg ){ assert( rc==SQLITE_OK ); *ppPage = pPg; return SQLITE_OK; } } if( rc!=SQLITE_OK ){ *ppPage = 0; return rc; } } return getPageNormal(pPager, pgno, ppPage, flags); } #endif /* SQLITE_MAX_MMAP_SIZE>0 */ /* The page getter method for when the pager is an error state */ static int getPageError( Pager *pPager, /* The pager open on the database file */ Pgno pgno, /* Page number to fetch */ DbPage **ppPage, /* Write a pointer to the page here */ int flags /* PAGER_GET_XXX flags */ ){ UNUSED_PARAMETER(pgno); UNUSED_PARAMETER(flags); assert( pPager->errCode!=SQLITE_OK ); *ppPage = 0; return pPager->errCode; } /* Dispatch all page fetch requests to the appropriate getter method. */ int sqlite3PagerGet( Pager *pPager, /* The pager open on the database file */ Pgno pgno, /* Page number to fetch */ DbPage **ppPage, /* Write a pointer to the page here */ int flags /* PAGER_GET_XXX flags */ ){ return pPager->xGet(pPager, pgno, ppPage, flags); } /* ** Acquire a page if it is already in the in-memory cache. Do ** not read the page from disk. Return a pointer to the page, ** or 0 if the page is not in cache. ** ** See also sqlite3PagerGet(). The difference between this routine ** and sqlite3PagerGet() is that _get() will go to the disk and read ** in the page if the page is not already in cache. This routine ** returns NULL if the page is not in cache or if a disk I/O error ** has ever happened. */ DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){ sqlite3_pcache_page *pPage; assert( pPager!=0 ); assert( pgno!=0 ); assert( pPager->pPCache!=0 ); pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0); assert( pPage==0 || pPager->hasHeldSharedLock ); if( pPage==0 ) return 0; return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage); } /* ** Release a page reference. ** ** The sqlite3PagerUnref() and sqlite3PagerUnrefNotNull() may only be ** used if we know that the page being released is not the last page. ** The btree layer always holds page1 open until the end, so these first ** to routines can be used to release any page other than BtShared.pPage1. ** ** Use sqlite3PagerUnrefPageOne() to release page1. This latter routine ** checks the total number of outstanding pages and if the number of ** pages reaches zero it drops the database lock. */ void sqlite3PagerUnrefNotNull(DbPage *pPg){ TESTONLY( Pager *pPager = pPg->pPager; ) assert( pPg!=0 ); if( pPg->flags & PGHDR_MMAP ){ assert( pPg->pgno!=1 ); /* Page1 is never memory mapped */ pagerReleaseMapPage(pPg); }else{ sqlite3PcacheRelease(pPg); } /* Do not use this routine to release the last reference to page1 */ assert( sqlite3PcacheRefCount(pPager->pPCache)>0 ); } void sqlite3PagerUnref(DbPage *pPg){ if( pPg ) sqlite3PagerUnrefNotNull(pPg); } void sqlite3PagerUnrefPageOne(DbPage *pPg){ Pager *pPager; assert( pPg!=0 ); assert( pPg->pgno==1 ); assert( (pPg->flags & PGHDR_MMAP)==0 ); /* Page1 is never memory mapped */ pPager = pPg->pPager; sqlite3PcacheRelease(pPg); pagerUnlockIfUnused(pPager); } /* ** This function is called at the start of every write transaction. ** There must already be a RESERVED or EXCLUSIVE lock on the database ** file when this routine is called. ** ** Open the journal file for pager pPager and write a journal header ** to the start of it. If there are active savepoints, open the sub-journal ** as well. This function is only used when the journal file is being ** opened to write a rollback log for a transaction. It is not used ** when opening a hot journal file to roll it back. ** ** If the journal file is already open (as it may be in exclusive mode), ** then this function just writes a journal header to the start of the ** already open file. ** ** Whether or not the journal file is opened by this function, the ** Pager.pInJournal bitvec structure is allocated. ** ** Return SQLITE_OK if everything is successful. Otherwise, return ** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or ** an IO error code if opening or writing the journal file fails. */ static int pager_open_journal(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ sqlite3_vfs * const pVfs = pPager->pVfs; /* Local cache of vfs pointer */ assert( pPager->eState==PAGER_WRITER_LOCKED ); assert( assert_pager_state(pPager) ); assert( pPager->pInJournal==0 ); /* If already in the error state, this function is a no-op. But on ** the other hand, this routine is never called if we are already in ** an error state. */ if( NEVER(pPager->errCode) ) return pPager->errCode; if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize); if( pPager->pInJournal==0 ){ return SQLITE_NOMEM_BKPT; } /* Open the journal file if it is not already open. */ if( !isOpen(pPager->jfd) ){ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){ sqlite3MemJournalOpen(pPager->jfd); }else{ int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE; int nSpill; if( pPager->tempFile ){ flags |= (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL); nSpill = sqlite3Config.nStmtSpill; }else{ flags |= SQLITE_OPEN_MAIN_JOURNAL; nSpill = jrnlBufferSize(pPager); } /* Verify that the database still has the same name as it did when ** it was originally opened. */ rc = databaseIsUnmoved(pPager); if( rc==SQLITE_OK ){ rc = sqlite3JournalOpen ( pVfs, pPager->zJournal, pPager->jfd, flags, nSpill ); } } assert( rc!=SQLITE_OK || isOpen(pPager->jfd) ); } /* Write the first journal header to the journal file and open ** the sub-journal if necessary. */ if( rc==SQLITE_OK ){ /* TODO: Check if all of these are really required. */ pPager->nRec = 0; pPager->journalOff = 0; pPager->setSuper = 0; pPager->journalHdr = 0; rc = writeJournalHdr(pPager); } } if( rc!=SQLITE_OK ){ sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; }else{ assert( pPager->eState==PAGER_WRITER_LOCKED ); pPager->eState = PAGER_WRITER_CACHEMOD; } return rc; } /* ** Begin a write-transaction on the specified pager object. If a ** write-transaction has already been opened, this function is a no-op. ** ** If the exFlag argument is false, then acquire at least a RESERVED ** lock on the database file. If exFlag is true, then acquire at least ** an EXCLUSIVE lock. If such a lock is already held, no locking ** functions need be called. ** ** If the subjInMemory argument is non-zero, then any sub-journal opened ** within this transaction will be opened as an in-memory file. This ** has no effect if the sub-journal is already opened (as it may be when ** running in exclusive mode) or if the transaction does not require a ** sub-journal. If the subjInMemory argument is zero, then any required ** sub-journal is implemented in-memory if pPager is an in-memory database, ** or using a temporary file otherwise. */ int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){ int rc = SQLITE_OK; if( pPager->errCode ) return pPager->errCode; assert( pPager->eState>=PAGER_READER && pPager->eStatesubjInMemory = (u8)subjInMemory; if( pPager->eState==PAGER_READER ){ assert( pPager->pInJournal==0 ); if( pagerUseWal(pPager) ){ /* If the pager is configured to use locking_mode=exclusive, and an ** exclusive lock on the database is not already held, obtain it now. */ if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){ rc = pagerLockDb(pPager, EXCLUSIVE_LOCK); if( rc!=SQLITE_OK ){ return rc; } (void)sqlite3WalExclusiveMode(pPager->pWal, 1); } /* Grab the write lock on the log file. If successful, upgrade to ** PAGER_RESERVED state. Otherwise, return an error code to the caller. ** The busy-handler is not invoked if another connection already ** holds the write-lock. If possible, the upper layer will call it. */ rc = sqlite3WalBeginWriteTransaction(pPager->pWal); }else{ /* Obtain a RESERVED lock on the database file. If the exFlag parameter ** is true, then immediately upgrade this to an EXCLUSIVE lock. The ** busy-handler callback can be used when upgrading to the EXCLUSIVE ** lock, but not when obtaining the RESERVED lock. */ rc = pagerLockDb(pPager, RESERVED_LOCK); if( rc==SQLITE_OK && exFlag ){ rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK); } } if( rc==SQLITE_OK ){ /* Change to WRITER_LOCKED state. ** ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD ** when it has an open transaction, but never to DBMOD or FINISHED. ** This is because in those states the code to roll back savepoint ** transactions may copy data from the sub-journal into the database ** file as well as into the page cache. Which would be incorrect in ** WAL mode. */ pPager->eState = PAGER_WRITER_LOCKED; pPager->dbHintSize = pPager->dbSize; pPager->dbFileSize = pPager->dbSize; pPager->dbOrigSize = pPager->dbSize; pPager->journalOff = 0; } assert( rc==SQLITE_OK || pPager->eState==PAGER_READER ); assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED ); assert( assert_pager_state(pPager) ); } PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager))); return rc; } /* ** Write page pPg onto the end of the rollback journal. */ static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){ Pager *pPager = pPg->pPager; int rc; u32 cksum; char *pData2; i64 iOff = pPager->journalOff; /* We should never write to the journal file the page that ** contains the database locks. The following assert verifies ** that we do not. */ assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) ); assert( pPager->journalHdr<=pPager->journalOff ); pData2 = pPg->pData; cksum = pager_cksum(pPager, (u8*)pData2); /* Even if an IO or diskfull error occurs while journalling the ** page in the block above, set the need-sync flag for the page. ** Otherwise, when the transaction is rolled back, the logic in ** playback_one_page() will think that the page needs to be restored ** in the database file. And if an IO error occurs while doing so, ** then corruption may follow. */ pPg->flags |= PGHDR_NEED_SYNC; rc = write32bits(pPager->jfd, iOff, pPg->pgno); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4); if( rc!=SQLITE_OK ) return rc; rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum); if( rc!=SQLITE_OK ) return rc; IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, pPager->journalOff, pPager->pageSize)); PAGER_INCR(sqlite3_pager_writej_count); PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n", PAGERID(pPager), pPg->pgno, ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg))); pPager->journalOff += 8 + pPager->pageSize; pPager->nRec++; assert( pPager->pInJournal!=0 ); rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno); testcase( rc==SQLITE_NOMEM ); assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); rc |= addToSavepointBitvecs(pPager, pPg->pgno); assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); return rc; } /* ** Mark a single data page as writeable. The page is written into the ** main journal or sub-journal as required. If the page is written into ** one of the journals, the corresponding bit is set in the ** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs ** of any open savepoints as appropriate. */ static int pager_write(PgHdr *pPg){ Pager *pPager = pPg->pPager; int rc = SQLITE_OK; /* This routine is not called unless a write-transaction has already ** been started. The journal file may or may not be open at this point. ** It is never called in the ERROR state. */ assert( pPager->eState==PAGER_WRITER_LOCKED || pPager->eState==PAGER_WRITER_CACHEMOD || pPager->eState==PAGER_WRITER_DBMOD ); assert( assert_pager_state(pPager) ); assert( pPager->errCode==0 ); assert( pPager->readOnly==0 ); CHECK_PAGE(pPg); /* The journal file needs to be opened. Higher level routines have already ** obtained the necessary locks to begin the write-transaction, but the ** rollback journal might not yet be open. Open it now if this is the case. ** ** This is done before calling sqlite3PcacheMakeDirty() on the page. ** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then ** an error might occur and the pager would end up in WRITER_LOCKED state ** with pages marked as dirty in the cache. */ if( pPager->eState==PAGER_WRITER_LOCKED ){ rc = pager_open_journal(pPager); if( rc!=SQLITE_OK ) return rc; } assert( pPager->eState>=PAGER_WRITER_CACHEMOD ); assert( assert_pager_state(pPager) ); /* Mark the page that is about to be modified as dirty. */ sqlite3PcacheMakeDirty(pPg); /* If a rollback journal is in use, them make sure the page that is about ** to change is in the rollback journal, or if the page is a new page off ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC. */ assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) ); if( pPager->pInJournal!=0 && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0 ){ assert( pagerUseWal(pPager)==0 ); if( pPg->pgno<=pPager->dbOrigSize ){ rc = pagerAddPageToRollbackJournal(pPg); if( rc!=SQLITE_OK ){ return rc; } }else{ if( pPager->eState!=PAGER_WRITER_DBMOD ){ pPg->flags |= PGHDR_NEED_SYNC; } PAGERTRACE(("APPEND %d page %d needSync=%d\n", PAGERID(pPager), pPg->pgno, ((pPg->flags&PGHDR_NEED_SYNC)?1:0))); } } /* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list ** and before writing the page into the rollback journal. Wait until now, ** after the page has been successfully journalled, before setting the ** PGHDR_WRITEABLE bit that indicates that the page can be safely modified. */ pPg->flags |= PGHDR_WRITEABLE; /* If the statement journal is open and the page is not in it, ** then write the page into the statement journal. */ if( pPager->nSavepoint>0 ){ rc = subjournalPageIfRequired(pPg); } /* Update the database size and return. */ if( pPager->dbSizepgno ){ pPager->dbSize = pPg->pgno; } return rc; } /* ** This is a variant of sqlite3PagerWrite() that runs when the sector size ** is larger than the page size. SQLite makes the (reasonable) assumption that ** all bytes of a sector are written together by hardware. Hence, all bytes of ** a sector need to be journalled in case of a power loss in the middle of ** a write. ** ** Usually, the sector size is less than or equal to the page size, in which ** case pages can be individually written. This routine only runs in the ** exceptional case where the page size is smaller than the sector size. */ static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){ int rc = SQLITE_OK; /* Return code */ Pgno nPageCount; /* Total number of pages in database file */ Pgno pg1; /* First page of the sector pPg is located on. */ int nPage = 0; /* Number of pages starting at pg1 to journal */ int ii; /* Loop counter */ int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */ Pager *pPager = pPg->pPager; /* The pager that owns pPg */ Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize); /* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow ** a journal header to be written between the pages journaled by ** this function. */ assert( !MEMDB ); assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)==0 ); pPager->doNotSpill |= SPILLFLAG_NOSYNC; /* This trick assumes that both the page-size and sector-size are ** an integer power of 2. It sets variable pg1 to the identifier ** of the first page of the sector pPg is located on. */ pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1; nPageCount = pPager->dbSize; if( pPg->pgno>nPageCount ){ nPage = (pPg->pgno - pg1)+1; }else if( (pg1+nPagePerSector-1)>nPageCount ){ nPage = nPageCount+1-pg1; }else{ nPage = nPagePerSector; } assert(nPage>0); assert(pg1<=pPg->pgno); assert((pg1+nPage)>pPg->pgno); for(ii=0; iipgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){ if( pg!=PAGER_MJ_PGNO(pPager) ){ rc = sqlite3PagerGet(pPager, pg, &pPage, 0); if( rc==SQLITE_OK ){ rc = pager_write(pPage); if( pPage->flags&PGHDR_NEED_SYNC ){ needSync = 1; } sqlite3PagerUnrefNotNull(pPage); } } }else if( (pPage = sqlite3PagerLookup(pPager, pg))!=0 ){ if( pPage->flags&PGHDR_NEED_SYNC ){ needSync = 1; } sqlite3PagerUnrefNotNull(pPage); } } /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages ** starting at pg1, then it needs to be set for all of them. Because ** writing to any of these nPage pages may damage the others, the ** journal file must contain sync()ed copies of all of them ** before any of them can be written out to the database file. */ if( rc==SQLITE_OK && needSync ){ assert( !MEMDB ); for(ii=0; iiflags |= PGHDR_NEED_SYNC; sqlite3PagerUnrefNotNull(pPage); } } } assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 ); pPager->doNotSpill &= ~SPILLFLAG_NOSYNC; return rc; } /* ** Mark a data page as writeable. This routine must be called before ** making changes to a page. The caller must check the return value ** of this function and be careful not to change any page data unless ** this routine returns SQLITE_OK. ** ** The difference between this function and pager_write() is that this ** function also deals with the special case where 2 or more pages ** fit on a single disk sector. In this case all co-resident pages ** must have been written to the journal file before returning. ** ** If an error occurs, SQLITE_NOMEM or an IO error code is returned ** as appropriate. Otherwise, SQLITE_OK. */ int sqlite3PagerWrite(PgHdr *pPg){ Pager *pPager = pPg->pPager; assert( (pPg->flags & PGHDR_MMAP)==0 ); assert( pPager->eState>=PAGER_WRITER_LOCKED ); assert( assert_pager_state(pPager) ); if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){ if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg); return SQLITE_OK; }else if( pPager->errCode ){ return pPager->errCode; }else if( pPager->sectorSize > (u32)pPager->pageSize ){ assert( pPager->tempFile==0 ); return pagerWriteLargeSector(pPg); }else{ return pager_write(pPg); } } /* ** Return TRUE if the page given in the argument was previously passed ** to sqlite3PagerWrite(). In other words, return TRUE if it is ok ** to change the content of the page. */ #ifndef NDEBUG int sqlite3PagerIswriteable(DbPage *pPg){ return pPg->flags & PGHDR_WRITEABLE; } #endif /* ** A call to this routine tells the pager that it is not necessary to ** write the information on page pPg back to the disk, even though ** that page might be marked as dirty. This happens, for example, when ** the page has been added as a leaf of the freelist and so its ** content no longer matters. ** ** The overlying software layer calls this routine when all of the data ** on the given page is unused. The pager marks the page as clean so ** that it does not get written to disk. ** ** Tests show that this optimization can quadruple the speed of large ** DELETE operations. ** ** This optimization cannot be used with a temp-file, as the page may ** have been dirty at the start of the transaction. In that case, if ** memory pressure forces page pPg out of the cache, the data does need ** to be written out to disk so that it may be read back in if the ** current transaction is rolled back. */ void sqlite3PagerDontWrite(PgHdr *pPg){ Pager *pPager = pPg->pPager; if( !pPager->tempFile && (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){ PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager))); IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno)) pPg->flags |= PGHDR_DONT_WRITE; pPg->flags &= ~PGHDR_WRITEABLE; testcase( pPg->flags & PGHDR_NEED_SYNC ); pager_set_pagehash(pPg); } } /* ** This routine is called to increment the value of the database file ** change-counter, stored as a 4-byte big-endian integer starting at ** byte offset 24 of the pager file. The secondary change counter at ** 92 is also updated, as is the SQLite version number at offset 96. ** ** But this only happens if the pPager->changeCountDone flag is false. ** To avoid excess churning of page 1, the update only happens once. ** See also the pager_write_changecounter() routine that does an ** unconditional update of the change counters. ** ** If the isDirectMode flag is zero, then this is done by calling ** sqlite3PagerWrite() on page 1, then modifying the contents of the ** page data. In this case the file will be updated when the current ** transaction is committed. ** ** The isDirectMode flag may only be non-zero if the library was compiled ** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case, ** if isDirect is non-zero, then the database file is updated directly ** by writing an updated version of page 1 using a call to the ** sqlite3OsWrite() function. */ static int pager_incr_changecounter(Pager *pPager, int isDirectMode){ int rc = SQLITE_OK; assert( pPager->eState==PAGER_WRITER_CACHEMOD || pPager->eState==PAGER_WRITER_DBMOD ); assert( assert_pager_state(pPager) ); /* Declare and initialize constant integer 'isDirect'. If the ** atomic-write optimization is enabled in this build, then isDirect ** is initialized to the value passed as the isDirectMode parameter ** to this function. Otherwise, it is always set to zero. ** ** The idea is that if the atomic-write optimization is not ** enabled at compile time, the compiler can omit the tests of ** 'isDirect' below, as well as the block enclosed in the ** "if( isDirect )" condition. */ #ifndef SQLITE_ENABLE_ATOMIC_WRITE # define DIRECT_MODE 0 assert( isDirectMode==0 ); UNUSED_PARAMETER(isDirectMode); #else # define DIRECT_MODE isDirectMode #endif if( !pPager->changeCountDone && ALWAYS(pPager->dbSize>0) ){ PgHdr *pPgHdr; /* Reference to page 1 */ assert( !pPager->tempFile && isOpen(pPager->fd) ); /* Open page 1 of the file for writing. */ rc = sqlite3PagerGet(pPager, 1, &pPgHdr, 0); assert( pPgHdr==0 || rc==SQLITE_OK ); /* If page one was fetched successfully, and this function is not ** operating in direct-mode, make page 1 writable. When not in ** direct mode, page 1 is always held in cache and hence the PagerGet() ** above is always successful - hence the ALWAYS on rc==SQLITE_OK. */ if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){ rc = sqlite3PagerWrite(pPgHdr); } if( rc==SQLITE_OK ){ /* Actually do the update of the change counter */ pager_write_changecounter(pPgHdr); /* If running in direct mode, write the contents of page 1 to the file. */ if( DIRECT_MODE ){ const void *zBuf; assert( pPager->dbFileSize>0 ); zBuf = pPgHdr->pData; if( rc==SQLITE_OK ){ rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0); pPager->aStat[PAGER_STAT_WRITE]++; } if( rc==SQLITE_OK ){ /* Update the pager's copy of the change-counter. Otherwise, the ** next time a read transaction is opened the cache will be ** flushed (as the change-counter values will not match). */ const void *pCopy = (const void *)&((const char *)zBuf)[24]; memcpy(&pPager->dbFileVers, pCopy, sizeof(pPager->dbFileVers)); pPager->changeCountDone = 1; } }else{ pPager->changeCountDone = 1; } } /* Release the page reference. */ sqlite3PagerUnref(pPgHdr); } return rc; } /* ** Sync the database file to disk. This is a no-op for in-memory databases ** or pages with the Pager.noSync flag set. ** ** If successful, or if called on a pager for which it is a no-op, this ** function returns SQLITE_OK. Otherwise, an IO error code is returned. */ int sqlite3PagerSync(Pager *pPager, const char *zSuper){ int rc = SQLITE_OK; void *pArg = (void*)zSuper; rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg); if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK; if( rc==SQLITE_OK && !pPager->noSync ){ assert( !MEMDB ); rc = sqlite3OsSync(pPager->fd, pPager->syncFlags); } return rc; } /* ** This function may only be called while a write-transaction is active in ** rollback. If the connection is in WAL mode, this call is a no-op. ** Otherwise, if the connection does not already have an EXCLUSIVE lock on ** the database file, an attempt is made to obtain one. ** ** If the EXCLUSIVE lock is already held or the attempt to obtain it is ** successful, or the connection is in WAL mode, SQLITE_OK is returned. ** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is ** returned. */ int sqlite3PagerExclusiveLock(Pager *pPager){ int rc = pPager->errCode; assert( assert_pager_state(pPager) ); if( rc==SQLITE_OK ){ assert( pPager->eState==PAGER_WRITER_CACHEMOD || pPager->eState==PAGER_WRITER_DBMOD || pPager->eState==PAGER_WRITER_LOCKED ); assert( assert_pager_state(pPager) ); if( 0==pagerUseWal(pPager) ){ rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK); } } return rc; } /* ** Sync the database file for the pager pPager. zSuper points to the name ** of a super-journal file that should be written into the individual ** journal file. zSuper may be NULL, which is interpreted as no ** super-journal (a single database transaction). ** ** This routine ensures that: ** ** * The database file change-counter is updated, ** * the journal is synced (unless the atomic-write optimization is used), ** * all dirty pages are written to the database file, ** * the database file is truncated (if required), and ** * the database file synced. ** ** The only thing that remains to commit the transaction is to finalize ** (delete, truncate or zero the first part of) the journal file (or ** delete the super-journal file if specified). ** ** Note that if zSuper==NULL, this does not overwrite a previous value ** passed to an sqlite3PagerCommitPhaseOne() call. ** ** If the final parameter - noSync - is true, then the database file itself ** is not synced. The caller must call sqlite3PagerSync() directly to ** sync the database file before calling CommitPhaseTwo() to delete the ** journal file in this case. */ int sqlite3PagerCommitPhaseOne( Pager *pPager, /* Pager object */ const char *zSuper, /* If not NULL, the super-journal name */ int noSync /* True to omit the xSync on the db file */ ){ int rc = SQLITE_OK; /* Return code */ assert( pPager->eState==PAGER_WRITER_LOCKED || pPager->eState==PAGER_WRITER_CACHEMOD || pPager->eState==PAGER_WRITER_DBMOD || pPager->eState==PAGER_ERROR ); assert( assert_pager_state(pPager) ); /* If a prior error occurred, report that error again. */ if( NEVER(pPager->errCode) ) return pPager->errCode; /* Provide the ability to easily simulate an I/O error during testing */ if( sqlite3FaultSim(400) ) return SQLITE_IOERR; PAGERTRACE(("DATABASE SYNC: File=%s zSuper=%s nSize=%d\n", pPager->zFilename, zSuper, pPager->dbSize)); /* If no database changes have been made, return early. */ if( pPager->eStatetempFile ); assert( isOpen(pPager->fd) || pPager->tempFile ); if( 0==pagerFlushOnCommit(pPager, 1) ){ /* If this is an in-memory db, or no pages have been written to, or this ** function has already been called, it is mostly a no-op. However, any ** backup in progress needs to be restarted. */ sqlite3BackupRestart(pPager->pBackup); }else{ PgHdr *pList; if( pagerUseWal(pPager) ){ PgHdr *pPageOne = 0; pList = sqlite3PcacheDirtyList(pPager->pPCache); if( pList==0 ){ /* Must have at least one page for the WAL commit flag. ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */ rc = sqlite3PagerGet(pPager, 1, &pPageOne, 0); pList = pPageOne; pList->pDirty = 0; } assert( rc==SQLITE_OK ); if( ALWAYS(pList) ){ rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1); } sqlite3PagerUnref(pPageOne); if( rc==SQLITE_OK ){ sqlite3PcacheCleanAll(pPager->pPCache); } }else{ /* The bBatch boolean is true if the batch-atomic-write commit method ** should be used. No rollback journal is created if batch-atomic-write ** is enabled. */ #ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE sqlite3_file *fd = pPager->fd; int bBatch = zSuper==0 /* An SQLITE_IOCAP_BATCH_ATOMIC commit */ && (sqlite3OsDeviceCharacteristics(fd) & SQLITE_IOCAP_BATCH_ATOMIC) && !pPager->noSync && sqlite3JournalIsInMemory(pPager->jfd); #else # define bBatch 0 #endif #ifdef SQLITE_ENABLE_ATOMIC_WRITE /* The following block updates the change-counter. Exactly how it ** does this depends on whether or not the atomic-update optimization ** was enabled at compile time, and if this transaction meets the ** runtime criteria to use the operation: ** ** * The file-system supports the atomic-write property for ** blocks of size page-size, and ** * This commit is not part of a multi-file transaction, and ** * Exactly one page has been modified and store in the journal file. ** ** If the optimization was not enabled at compile time, then the ** pager_incr_changecounter() function is called to update the change ** counter in 'indirect-mode'. If the optimization is compiled in but ** is not applicable to this transaction, call sqlite3JournalCreate() ** to make sure the journal file has actually been created, then call ** pager_incr_changecounter() to update the change-counter in indirect ** mode. ** ** Otherwise, if the optimization is both enabled and applicable, ** then call pager_incr_changecounter() to update the change-counter ** in 'direct' mode. In this case the journal file will never be ** created for this transaction. */ if( bBatch==0 ){ PgHdr *pPg; assert( isOpen(pPager->jfd) || pPager->journalMode==PAGER_JOURNALMODE_OFF || pPager->journalMode==PAGER_JOURNALMODE_WAL ); if( !zSuper && isOpen(pPager->jfd) && pPager->journalOff==jrnlBufferSize(pPager) && pPager->dbSize>=pPager->dbOrigSize && (!(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty) ){ /* Update the db file change counter via the direct-write method. The ** following call will modify the in-memory representation of page 1 ** to include the updated change counter and then write page 1 ** directly to the database file. Because of the atomic-write ** property of the host file-system, this is safe. */ rc = pager_incr_changecounter(pPager, 1); }else{ rc = sqlite3JournalCreate(pPager->jfd); if( rc==SQLITE_OK ){ rc = pager_incr_changecounter(pPager, 0); } } } #else /* SQLITE_ENABLE_ATOMIC_WRITE */ #ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE if( zSuper ){ rc = sqlite3JournalCreate(pPager->jfd); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; assert( bBatch==0 ); } #endif rc = pager_incr_changecounter(pPager, 0); #endif /* !SQLITE_ENABLE_ATOMIC_WRITE */ if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* Write the super-journal name into the journal file. If a ** super-journal file name has already been written to the journal file, ** or if zSuper is NULL (no super-journal), then this call is a no-op. */ rc = writeSuperJournal(pPager, zSuper); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* Sync the journal file and write all dirty pages to the database. ** If the atomic-update optimization is being used, this sync will not ** create the journal file or perform any real IO. ** ** Because the change-counter page was just modified, unless the ** atomic-update optimization is used it is almost certain that the ** journal requires a sync here. However, in locking_mode=exclusive ** on a system under memory pressure it is just possible that this is ** not the case. In this case it is likely enough that the redundant ** xSync() call will be changed to a no-op by the OS anyhow. */ rc = syncJournal(pPager, 0); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; pList = sqlite3PcacheDirtyList(pPager->pPCache); #ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE if( bBatch ){ rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_BEGIN_ATOMIC_WRITE, 0); if( rc==SQLITE_OK ){ rc = pager_write_pagelist(pPager, pList); if( rc==SQLITE_OK ){ rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_COMMIT_ATOMIC_WRITE, 0); } if( rc!=SQLITE_OK ){ sqlite3OsFileControlHint(fd, SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE, 0); } } if( (rc&0xFF)==SQLITE_IOERR && rc!=SQLITE_IOERR_NOMEM ){ rc = sqlite3JournalCreate(pPager->jfd); if( rc!=SQLITE_OK ){ sqlite3OsClose(pPager->jfd); goto commit_phase_one_exit; } bBatch = 0; }else{ sqlite3OsClose(pPager->jfd); } } #endif /* SQLITE_ENABLE_BATCH_ATOMIC_WRITE */ if( bBatch==0 ){ rc = pager_write_pagelist(pPager, pList); } if( rc!=SQLITE_OK ){ assert( rc!=SQLITE_IOERR_BLOCKED ); goto commit_phase_one_exit; } sqlite3PcacheCleanAll(pPager->pPCache); /* If the file on disk is smaller than the database image, use ** pager_truncate to grow the file here. This can happen if the database ** image was extended as part of the current transaction and then the ** last page in the db image moved to the free-list. In this case the ** last page is never written out to disk, leaving the database file ** undersized. Fix this now if it is the case. */ if( pPager->dbSize>pPager->dbFileSize ){ Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager)); assert( pPager->eState==PAGER_WRITER_DBMOD ); rc = pager_truncate(pPager, nNew); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; } /* Finally, sync the database file. */ if( !noSync ){ rc = sqlite3PagerSync(pPager, zSuper); } IOTRACE(("DBSYNC %p\n", pPager)) } } commit_phase_one_exit: if( rc==SQLITE_OK && !pagerUseWal(pPager) ){ pPager->eState = PAGER_WRITER_FINISHED; } return rc; } /* ** When this function is called, the database file has been completely ** updated to reflect the changes made by the current transaction and ** synced to disk. The journal file still exists in the file-system ** though, and if a failure occurs at this point it will eventually ** be used as a hot-journal and the current transaction rolled back. ** ** This function finalizes the journal file, either by deleting, ** truncating or partially zeroing it, so that it cannot be used ** for hot-journal rollback. Once this is done the transaction is ** irrevocably committed. ** ** If an error occurs, an IO error code is returned and the pager ** moves into the error state. Otherwise, SQLITE_OK is returned. */ int sqlite3PagerCommitPhaseTwo(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ /* This routine should not be called if a prior error has occurred. ** But if (due to a coding error elsewhere in the system) it does get ** called, just return the same error code without doing anything. */ if( NEVER(pPager->errCode) ) return pPager->errCode; pPager->iDataVersion++; assert( pPager->eState==PAGER_WRITER_LOCKED || pPager->eState==PAGER_WRITER_FINISHED || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD) ); assert( assert_pager_state(pPager) ); /* An optimization. If the database was not actually modified during ** this transaction, the pager is running in exclusive-mode and is ** using persistent journals, then this function is a no-op. ** ** The start of the journal file currently contains a single journal ** header with the nRec field set to 0. If such a journal is used as ** a hot-journal during hot-journal rollback, 0 changes will be made ** to the database file. So there is no need to zero the journal ** header. Since the pager is in exclusive mode, there is no need ** to drop any locks either. */ if( pPager->eState==PAGER_WRITER_LOCKED && pPager->exclusiveMode && pPager->journalMode==PAGER_JOURNALMODE_PERSIST ){ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff ); pPager->eState = PAGER_READER; return SQLITE_OK; } PAGERTRACE(("COMMIT %d\n", PAGERID(pPager))); rc = pager_end_transaction(pPager, pPager->setSuper, 1); return pager_error(pPager, rc); } /* ** If a write transaction is open, then all changes made within the ** transaction are reverted and the current write-transaction is closed. ** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR ** state if an error occurs. ** ** If the pager is already in PAGER_ERROR state when this function is called, ** it returns Pager.errCode immediately. No work is performed in this case. ** ** Otherwise, in rollback mode, this function performs two functions: ** ** 1) It rolls back the journal file, restoring all database file and ** in-memory cache pages to the state they were in when the transaction ** was opened, and ** ** 2) It finalizes the journal file, so that it is not used for hot ** rollback at any point in the future. ** ** Finalization of the journal file (task 2) is only performed if the ** rollback is successful. ** ** In WAL mode, all cache-entries containing data modified within the ** current transaction are either expelled from the cache or reverted to ** their pre-transaction state by re-reading data from the database or ** WAL files. The WAL transaction is then closed. */ int sqlite3PagerRollback(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager))); /* PagerRollback() is a no-op if called in READER or OPEN state. If ** the pager is already in the ERROR state, the rollback is not ** attempted here. Instead, the error code is returned to the caller. */ assert( assert_pager_state(pPager) ); if( pPager->eState==PAGER_ERROR ) return pPager->errCode; if( pPager->eState<=PAGER_READER ) return SQLITE_OK; if( pagerUseWal(pPager) ){ int rc2; rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1); rc2 = pager_end_transaction(pPager, pPager->setSuper, 0); if( rc==SQLITE_OK ) rc = rc2; }else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){ int eState = pPager->eState; rc = pager_end_transaction(pPager, 0, 0); if( !MEMDB && eState>PAGER_WRITER_LOCKED ){ /* This can happen using journal_mode=off. Move the pager to the error ** state to indicate that the contents of the cache may not be trusted. ** Any active readers will get SQLITE_ABORT. */ pPager->errCode = SQLITE_ABORT; pPager->eState = PAGER_ERROR; setGetterMethod(pPager); return rc; } }else{ rc = pager_playback(pPager, 0); } assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK ); assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR || rc==SQLITE_CANTOPEN ); /* If an error occurs during a ROLLBACK, we can no longer trust the pager ** cache. So call pager_error() on the way out to make any error persistent. */ return pager_error(pPager, rc); } /* ** Return TRUE if the database file is opened read-only. Return FALSE ** if the database is (in theory) writable. */ u8 sqlite3PagerIsreadonly(Pager *pPager){ return pPager->readOnly; } #ifdef SQLITE_DEBUG /* ** Return the sum of the reference counts for all pages held by pPager. */ int sqlite3PagerRefcount(Pager *pPager){ return sqlite3PcacheRefCount(pPager->pPCache); } #endif /* ** Return the approximate number of bytes of memory currently ** used by the pager and its associated cache. */ int sqlite3PagerMemUsed(Pager *pPager){ int perPageSize = pPager->pageSize + pPager->nExtra + (int)(sizeof(PgHdr) + 5*sizeof(void*)); return perPageSize*sqlite3PcachePagecount(pPager->pPCache) + sqlite3MallocSize(pPager) + pPager->pageSize; } /* ** Return the number of references to the specified page. */ int sqlite3PagerPageRefcount(DbPage *pPage){ return sqlite3PcachePageRefcount(pPage); } #ifdef SQLITE_TEST /* ** This routine is used for testing and analysis only. */ int *sqlite3PagerStats(Pager *pPager){ static int a[11]; a[0] = sqlite3PcacheRefCount(pPager->pPCache); a[1] = sqlite3PcachePagecount(pPager->pPCache); a[2] = sqlite3PcacheGetCachesize(pPager->pPCache); a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize; a[4] = pPager->eState; a[5] = pPager->errCode; a[6] = pPager->aStat[PAGER_STAT_HIT]; a[7] = pPager->aStat[PAGER_STAT_MISS]; a[8] = 0; /* Used to be pPager->nOvfl */ a[9] = pPager->nRead; a[10] = pPager->aStat[PAGER_STAT_WRITE]; return a; } #endif /* ** Parameter eStat must be one of SQLITE_DBSTATUS_CACHE_HIT, _MISS, _WRITE, ** or _WRITE+1. The SQLITE_DBSTATUS_CACHE_WRITE+1 case is a translation ** of SQLITE_DBSTATUS_CACHE_SPILL. The _SPILL case is not contiguous because ** it was added later. ** ** Before returning, *pnVal is incremented by the ** current cache hit or miss count, according to the value of eStat. If the ** reset parameter is non-zero, the cache hit or miss count is zeroed before ** returning. */ void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, int *pnVal){ assert( eStat==SQLITE_DBSTATUS_CACHE_HIT || eStat==SQLITE_DBSTATUS_CACHE_MISS || eStat==SQLITE_DBSTATUS_CACHE_WRITE || eStat==SQLITE_DBSTATUS_CACHE_WRITE+1 ); assert( SQLITE_DBSTATUS_CACHE_HIT+1==SQLITE_DBSTATUS_CACHE_MISS ); assert( SQLITE_DBSTATUS_CACHE_HIT+2==SQLITE_DBSTATUS_CACHE_WRITE ); assert( PAGER_STAT_HIT==0 && PAGER_STAT_MISS==1 && PAGER_STAT_WRITE==2 && PAGER_STAT_SPILL==3 ); eStat -= SQLITE_DBSTATUS_CACHE_HIT; *pnVal += pPager->aStat[eStat]; if( reset ){ pPager->aStat[eStat] = 0; } } /* ** Return true if this is an in-memory or temp-file backed pager. */ int sqlite3PagerIsMemdb(Pager *pPager){ return pPager->tempFile || pPager->memVfs; } /* ** Check that there are at least nSavepoint savepoints open. If there are ** currently less than nSavepoints open, then open one or more savepoints ** to make up the difference. If the number of savepoints is already ** equal to nSavepoint, then this function is a no-op. ** ** If a memory allocation fails, SQLITE_NOMEM is returned. If an error ** occurs while opening the sub-journal file, then an IO error code is ** returned. Otherwise, SQLITE_OK. */ static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){ int rc = SQLITE_OK; /* Return code */ int nCurrent = pPager->nSavepoint; /* Current number of savepoints */ int ii; /* Iterator variable */ PagerSavepoint *aNew; /* New Pager.aSavepoint array */ assert( pPager->eState>=PAGER_WRITER_LOCKED ); assert( assert_pager_state(pPager) ); assert( nSavepoint>nCurrent && pPager->useJournal ); /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM ** if the allocation fails. Otherwise, zero the new portion in case a ** malloc failure occurs while populating it in the for(...) loop below. */ aNew = (PagerSavepoint *)sqlite3Realloc( pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint ); if( !aNew ){ return SQLITE_NOMEM_BKPT; } memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint)); pPager->aSavepoint = aNew; /* Populate the PagerSavepoint structures just allocated. */ for(ii=nCurrent; iidbSize; if( isOpen(pPager->jfd) && pPager->journalOff>0 ){ aNew[ii].iOffset = pPager->journalOff; }else{ aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager); } aNew[ii].iSubRec = pPager->nSubRec; aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize); aNew[ii].bTruncateOnRelease = 1; if( !aNew[ii].pInSavepoint ){ return SQLITE_NOMEM_BKPT; } if( pagerUseWal(pPager) ){ sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData); } pPager->nSavepoint = ii+1; } assert( pPager->nSavepoint==nSavepoint ); assertTruncateConstraint(pPager); return rc; } int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){ assert( pPager->eState>=PAGER_WRITER_LOCKED ); assert( assert_pager_state(pPager) ); if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){ return pagerOpenSavepoint(pPager, nSavepoint); }else{ return SQLITE_OK; } } /* ** This function is called to rollback or release (commit) a savepoint. ** The savepoint to release or rollback need not be the most recently ** created savepoint. ** ** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE. ** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with ** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes ** that have occurred since the specified savepoint was created. ** ** The savepoint to rollback or release is identified by parameter ** iSavepoint. A value of 0 means to operate on the outermost savepoint ** (the first created). A value of (Pager.nSavepoint-1) means operate ** on the most recently created savepoint. If iSavepoint is greater than ** (Pager.nSavepoint-1), then this function is a no-op. ** ** If a negative value is passed to this function, then the current ** transaction is rolled back. This is different to calling ** sqlite3PagerRollback() because this function does not terminate ** the transaction or unlock the database, it just restores the ** contents of the database to its original state. ** ** In any case, all savepoints with an index greater than iSavepoint ** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE), ** then savepoint iSavepoint is also destroyed. ** ** This function may return SQLITE_NOMEM if a memory allocation fails, ** or an IO error code if an IO error occurs while rolling back a ** savepoint. If no errors occur, SQLITE_OK is returned. */ int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){ int rc = pPager->errCode; #ifdef SQLITE_ENABLE_ZIPVFS if( op==SAVEPOINT_RELEASE ) rc = SQLITE_OK; #endif assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK ); assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK ); if( rc==SQLITE_OK && iSavepointnSavepoint ){ int ii; /* Iterator variable */ int nNew; /* Number of remaining savepoints after this op. */ /* Figure out how many savepoints will still be active after this ** operation. Store this value in nNew. Then free resources associated ** with any savepoints that are destroyed by this operation. */ nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1); for(ii=nNew; iinSavepoint; ii++){ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); } pPager->nSavepoint = nNew; /* Truncate the sub-journal so that it only includes the parts ** that are still in use. */ if( op==SAVEPOINT_RELEASE ){ PagerSavepoint *pRel = &pPager->aSavepoint[nNew]; if( pRel->bTruncateOnRelease && isOpen(pPager->sjfd) ){ /* Only truncate if it is an in-memory sub-journal. */ if( sqlite3JournalIsInMemory(pPager->sjfd) ){ i64 sz = (pPager->pageSize+4)*(i64)pRel->iSubRec; rc = sqlite3OsTruncate(pPager->sjfd, sz); assert( rc==SQLITE_OK ); } pPager->nSubRec = pRel->iSubRec; } } /* Else this is a rollback operation, playback the specified savepoint. ** If this is a temp-file, it is possible that the journal file has ** not yet been opened. In this case there have been no changes to ** the database file, so the playback operation can be skipped. */ else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){ PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1]; rc = pagerPlaybackSavepoint(pPager, pSavepoint); assert(rc!=SQLITE_DONE); } #ifdef SQLITE_ENABLE_ZIPVFS /* If the cache has been modified but the savepoint cannot be rolled ** back journal_mode=off, put the pager in the error state. This way, ** if the VFS used by this pager includes ZipVFS, the entire transaction ** can be rolled back at the ZipVFS level. */ else if( pPager->journalMode==PAGER_JOURNALMODE_OFF && pPager->eState>=PAGER_WRITER_CACHEMOD ){ pPager->errCode = SQLITE_ABORT; pPager->eState = PAGER_ERROR; setGetterMethod(pPager); } #endif } return rc; } /* ** Return the full pathname of the database file. ** ** Except, if the pager is in-memory only, then return an empty string if ** nullIfMemDb is true. This routine is called with nullIfMemDb==1 when ** used to report the filename to the user, for compatibility with legacy ** behavior. But when the Btree needs to know the filename for matching to ** shared cache, it uses nullIfMemDb==0 so that in-memory databases can ** participate in shared-cache. ** ** The return value to this routine is always safe to use with ** sqlite3_uri_parameter() and sqlite3_filename_database() and friends. */ const char *sqlite3PagerFilename(const Pager *pPager, int nullIfMemDb){ static const char zFake[8] = { 0, 0, 0, 0, 0, 0, 0, 0 }; return (nullIfMemDb && pPager->memDb) ? &zFake[4] : pPager->zFilename; } /* ** Return the VFS structure for the pager. */ sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){ return pPager->pVfs; } /* ** Return the file handle for the database file associated ** with the pager. This might return NULL if the file has ** not yet been opened. */ sqlite3_file *sqlite3PagerFile(Pager *pPager){ return pPager->fd; } /* ** Return the file handle for the journal file (if it exists). ** This will be either the rollback journal or the WAL file. */ sqlite3_file *sqlite3PagerJrnlFile(Pager *pPager){ #if SQLITE_OMIT_WAL return pPager->jfd; #else return pPager->pWal ? sqlite3WalFile(pPager->pWal) : pPager->jfd; #endif } /* ** Return the full pathname of the journal file. */ const char *sqlite3PagerJournalname(Pager *pPager){ return pPager->zJournal; } #ifndef SQLITE_OMIT_AUTOVACUUM /* ** Move the page pPg to location pgno in the file. ** ** There must be no references to the page previously located at ** pgno (which we call pPgOld) though that page is allowed to be ** in cache. If the page previously located at pgno is not already ** in the rollback journal, it is not put there by by this routine. ** ** References to the page pPg remain valid. Updating any ** meta-data associated with pPg (i.e. data stored in the nExtra bytes ** allocated along with the page) is the responsibility of the caller. ** ** A transaction must be active when this routine is called. It used to be ** required that a statement transaction was not active, but this restriction ** has been removed (CREATE INDEX needs to move a page when a statement ** transaction is active). ** ** If the fourth argument, isCommit, is non-zero, then this page is being ** moved as part of a database reorganization just before the transaction ** is being committed. In this case, it is guaranteed that the database page ** pPg refers to will not be written to again within this transaction. ** ** This function may return SQLITE_NOMEM or an IO error code if an error ** occurs. Otherwise, it returns SQLITE_OK. */ int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){ PgHdr *pPgOld; /* The page being overwritten. */ Pgno needSyncPgno = 0; /* Old value of pPg->pgno, if sync is required */ int rc; /* Return code */ Pgno origPgno; /* The original page number */ assert( pPg->nRef>0 ); assert( pPager->eState==PAGER_WRITER_CACHEMOD || pPager->eState==PAGER_WRITER_DBMOD ); assert( assert_pager_state(pPager) ); /* In order to be able to rollback, an in-memory database must journal ** the page we are moving from. */ assert( pPager->tempFile || !MEMDB ); if( pPager->tempFile ){ rc = sqlite3PagerWrite(pPg); if( rc ) return rc; } /* If the page being moved is dirty and has not been saved by the latest ** savepoint, then save the current contents of the page into the ** sub-journal now. This is required to handle the following scenario: ** ** BEGIN; ** ** SAVEPOINT one; ** ** ROLLBACK TO one; ** ** If page X were not written to the sub-journal here, it would not ** be possible to restore its contents when the "ROLLBACK TO one" ** statement were is processed. ** ** subjournalPage() may need to allocate space to store pPg->pgno into ** one or more savepoint bitvecs. This is the reason this function ** may return SQLITE_NOMEM. */ if( (pPg->flags & PGHDR_DIRTY)!=0 && SQLITE_OK!=(rc = subjournalPageIfRequired(pPg)) ){ return rc; } PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n", PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno)); IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno)) /* If the journal needs to be sync()ed before page pPg->pgno can ** be written to, store pPg->pgno in local variable needSyncPgno. ** ** If the isCommit flag is set, there is no need to remember that ** the journal needs to be sync()ed before database page pPg->pgno ** can be written to. The caller has already promised not to write to it. */ if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){ needSyncPgno = pPg->pgno; assert( pPager->journalMode==PAGER_JOURNALMODE_OFF || pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize ); assert( pPg->flags&PGHDR_DIRTY ); } /* If the cache contains a page with page-number pgno, remove it ** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for ** page pgno before the 'move' operation, it needs to be retained ** for the page moved there. */ pPg->flags &= ~PGHDR_NEED_SYNC; pPgOld = sqlite3PagerLookup(pPager, pgno); assert( !pPgOld || pPgOld->nRef==1 || CORRUPT_DB ); if( pPgOld ){ if( NEVER(pPgOld->nRef>1) ){ sqlite3PagerUnrefNotNull(pPgOld); return SQLITE_CORRUPT_BKPT; } pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC); if( pPager->tempFile ){ /* Do not discard pages from an in-memory database since we might ** need to rollback later. Just move the page out of the way. */ sqlite3PcacheMove(pPgOld, pPager->dbSize+1); }else{ sqlite3PcacheDrop(pPgOld); } } origPgno = pPg->pgno; sqlite3PcacheMove(pPg, pgno); sqlite3PcacheMakeDirty(pPg); /* For an in-memory database, make sure the original page continues ** to exist, in case the transaction needs to roll back. Use pPgOld ** as the original page since it has already been allocated. */ if( pPager->tempFile && pPgOld ){ sqlite3PcacheMove(pPgOld, origPgno); sqlite3PagerUnrefNotNull(pPgOld); } if( needSyncPgno ){ /* If needSyncPgno is non-zero, then the journal file needs to be ** sync()ed before any data is written to database file page needSyncPgno. ** Currently, no such page exists in the page-cache and the ** "is journaled" bitvec flag has been set. This needs to be remedied by ** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC ** flag. ** ** If the attempt to load the page into the page-cache fails, (due ** to a malloc() or IO failure), clear the bit in the pInJournal[] ** array. Otherwise, if the page is loaded and written again in ** this transaction, it may be written to the database file before ** it is synced into the journal file. This way, it may end up in ** the journal file twice, but that is not a problem. */ PgHdr *pPgHdr; rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr, 0); if( rc!=SQLITE_OK ){ if( needSyncPgno<=pPager->dbOrigSize ){ assert( pPager->pTmpSpace!=0 ); sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace); } return rc; } pPgHdr->flags |= PGHDR_NEED_SYNC; sqlite3PcacheMakeDirty(pPgHdr); sqlite3PagerUnrefNotNull(pPgHdr); } return SQLITE_OK; } #endif /* ** The page handle passed as the first argument refers to a dirty page ** with a page number other than iNew. This function changes the page's ** page number to iNew and sets the value of the PgHdr.flags field to ** the value passed as the third parameter. */ void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){ assert( pPg->pgno!=iNew ); pPg->flags = flags; sqlite3PcacheMove(pPg, iNew); } /* ** Return a pointer to the data for the specified page. */ void *sqlite3PagerGetData(DbPage *pPg){ assert( pPg->nRef>0 || pPg->pPager->memDb ); return pPg->pData; } /* ** Return a pointer to the Pager.nExtra bytes of "extra" space ** allocated along with the specified page. */ void *sqlite3PagerGetExtra(DbPage *pPg){ return pPg->pExtra; } /* ** Get/set the locking-mode for this pager. Parameter eMode must be one ** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or ** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then ** the locking-mode is set to the value specified. ** ** The returned value is either PAGER_LOCKINGMODE_NORMAL or ** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated) ** locking-mode. */ int sqlite3PagerLockingMode(Pager *pPager, int eMode){ assert( eMode==PAGER_LOCKINGMODE_QUERY || eMode==PAGER_LOCKINGMODE_NORMAL || eMode==PAGER_LOCKINGMODE_EXCLUSIVE ); assert( PAGER_LOCKINGMODE_QUERY<0 ); assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 ); assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) ); if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){ pPager->exclusiveMode = (u8)eMode; } return (int)pPager->exclusiveMode; } /* ** Set the journal-mode for this pager. Parameter eMode must be one of: ** ** PAGER_JOURNALMODE_DELETE ** PAGER_JOURNALMODE_TRUNCATE ** PAGER_JOURNALMODE_PERSIST ** PAGER_JOURNALMODE_OFF ** PAGER_JOURNALMODE_MEMORY ** PAGER_JOURNALMODE_WAL ** ** The journalmode is set to the value specified if the change is allowed. ** The change may be disallowed for the following reasons: ** ** * An in-memory database can only have its journal_mode set to _OFF ** or _MEMORY. ** ** * Temporary databases cannot have _WAL journalmode. ** ** The returned indicate the current (possibly updated) journal-mode. */ int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){ u8 eOld = pPager->journalMode; /* Prior journalmode */ /* The eMode parameter is always valid */ assert( eMode==PAGER_JOURNALMODE_DELETE || eMode==PAGER_JOURNALMODE_TRUNCATE || eMode==PAGER_JOURNALMODE_PERSIST || eMode==PAGER_JOURNALMODE_OFF || eMode==PAGER_JOURNALMODE_WAL || eMode==PAGER_JOURNALMODE_MEMORY ); /* This routine is only called from the OP_JournalMode opcode, and ** the logic there will never allow a temporary file to be changed ** to WAL mode. */ assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL ); /* Do allow the journalmode of an in-memory database to be set to ** anything other than MEMORY or OFF */ if( MEMDB ){ assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF ); if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){ eMode = eOld; } } if( eMode!=eOld ){ /* Change the journal mode. */ assert( pPager->eState!=PAGER_ERROR ); pPager->journalMode = (u8)eMode; /* When transistioning from TRUNCATE or PERSIST to any other journal ** mode except WAL, unless the pager is in locking_mode=exclusive mode, ** delete the journal file. */ assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 ); assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 ); assert( (PAGER_JOURNALMODE_DELETE & 5)==0 ); assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 ); assert( (PAGER_JOURNALMODE_OFF & 5)==0 ); assert( (PAGER_JOURNALMODE_WAL & 5)==5 ); assert( isOpen(pPager->fd) || pPager->exclusiveMode ); if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){ /* In this case we would like to delete the journal file. If it is ** not possible, then that is not a problem. Deleting the journal file ** here is an optimization only. ** ** Before deleting the journal file, obtain a RESERVED lock on the ** database file. This ensures that the journal file is not deleted ** while it is in use by some other client. */ sqlite3OsClose(pPager->jfd); if( pPager->eLock>=RESERVED_LOCK ){ sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); }else{ int rc = SQLITE_OK; int state = pPager->eState; assert( state==PAGER_OPEN || state==PAGER_READER ); if( state==PAGER_OPEN ){ rc = sqlite3PagerSharedLock(pPager); } if( pPager->eState==PAGER_READER ){ assert( rc==SQLITE_OK ); rc = pagerLockDb(pPager, RESERVED_LOCK); } if( rc==SQLITE_OK ){ sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); } if( rc==SQLITE_OK && state==PAGER_READER ){ pagerUnlockDb(pPager, SHARED_LOCK); }else if( state==PAGER_OPEN ){ pager_unlock(pPager); } assert( state==pPager->eState ); } }else if( eMode==PAGER_JOURNALMODE_OFF ){ sqlite3OsClose(pPager->jfd); } } /* Return the new journal mode */ return (int)pPager->journalMode; } /* ** Return the current journal mode. */ int sqlite3PagerGetJournalMode(Pager *pPager){ return (int)pPager->journalMode; } /* ** Return TRUE if the pager is in a state where it is OK to change the ** journalmode. Journalmode changes can only happen when the database ** is unmodified. */ int sqlite3PagerOkToChangeJournalMode(Pager *pPager){ assert( assert_pager_state(pPager) ); if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0; if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0; return 1; } /* ** Get/set the size-limit used for persistent journal files. ** ** Setting the size limit to -1 means no limit is enforced. ** An attempt to set a limit smaller than -1 is a no-op. */ i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){ if( iLimit>=-1 ){ pPager->journalSizeLimit = iLimit; sqlite3WalLimit(pPager->pWal, iLimit); } return pPager->journalSizeLimit; } /* ** Return a pointer to the pPager->pBackup variable. The backup module ** in backup.c maintains the content of this variable. This module ** uses it opaquely as an argument to sqlite3BackupRestart() and ** sqlite3BackupUpdate() only. */ sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){ return &pPager->pBackup; } #ifndef SQLITE_OMIT_VACUUM /* ** Unless this is an in-memory or temporary database, clear the pager cache. */ void sqlite3PagerClearCache(Pager *pPager){ assert( MEMDB==0 || pPager->tempFile ); if( pPager->tempFile==0 ) pager_reset(pPager); } #endif #ifndef SQLITE_OMIT_WAL /* ** This function is called when the user invokes "PRAGMA wal_checkpoint", ** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint() ** or wal_blocking_checkpoint() API functions. ** ** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART. */ int sqlite3PagerCheckpoint( Pager *pPager, /* Checkpoint on this pager */ sqlite3 *db, /* Db handle used to check for interrupts */ int eMode, /* Type of checkpoint */ int *pnLog, /* OUT: Final number of frames in log */ int *pnCkpt /* OUT: Final number of checkpointed frames */ ){ int rc = SQLITE_OK; if( pPager->pWal ){ rc = sqlite3WalCheckpoint(pPager->pWal, db, eMode, (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler), pPager->pBusyHandlerArg, pPager->walSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace, pnLog, pnCkpt ); } return rc; } int sqlite3PagerWalCallback(Pager *pPager){ return sqlite3WalCallback(pPager->pWal); } /* ** Return true if the underlying VFS for the given pager supports the ** primitives necessary for write-ahead logging. */ int sqlite3PagerWalSupported(Pager *pPager){ const sqlite3_io_methods *pMethods = pPager->fd->pMethods; if( pPager->noLock ) return 0; return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap); } /* ** Attempt to take an exclusive lock on the database file. If a PENDING lock ** is obtained instead, immediately release it. */ static int pagerExclusiveLock(Pager *pPager){ int rc; /* Return code */ assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK ); rc = pagerLockDb(pPager, EXCLUSIVE_LOCK); if( rc!=SQLITE_OK ){ /* If the attempt to grab the exclusive lock failed, release the ** pending lock that may have been obtained instead. */ pagerUnlockDb(pPager, SHARED_LOCK); } return rc; } /* ** Call sqlite3WalOpen() to open the WAL handle. If the pager is in ** exclusive-locking mode when this function is called, take an EXCLUSIVE ** lock on the database file and use heap-memory to store the wal-index ** in. Otherwise, use the normal shared-memory. */ static int pagerOpenWal(Pager *pPager){ int rc = SQLITE_OK; assert( pPager->pWal==0 && pPager->tempFile==0 ); assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK ); /* If the pager is already in exclusive-mode, the WAL module will use ** heap-memory for the wal-index instead of the VFS shared-memory ** implementation. Take the exclusive lock now, before opening the WAL ** file, to make sure this is safe. */ if( pPager->exclusiveMode ){ rc = pagerExclusiveLock(pPager); } /* Open the connection to the log file. If this operation fails, ** (e.g. due to malloc() failure), return an error code. */ if( rc==SQLITE_OK ){ rc = sqlite3WalOpen(pPager->pVfs, pPager->fd, pPager->zWal, pPager->exclusiveMode, pPager->journalSizeLimit, &pPager->pWal ); } pagerFixMaplimit(pPager); return rc; } /* ** The caller must be holding a SHARED lock on the database file to call ** this function. ** ** If the pager passed as the first argument is open on a real database ** file (not a temp file or an in-memory database), and the WAL file ** is not already open, make an attempt to open it now. If successful, ** return SQLITE_OK. If an error occurs or the VFS used by the pager does ** not support the xShmXXX() methods, return an error code. *pbOpen is ** not modified in either case. ** ** If the pager is open on a temp-file (or in-memory database), or if ** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK ** without doing anything. */ int sqlite3PagerOpenWal( Pager *pPager, /* Pager object */ int *pbOpen /* OUT: Set to true if call is a no-op */ ){ int rc = SQLITE_OK; /* Return code */ assert( assert_pager_state(pPager) ); assert( pPager->eState==PAGER_OPEN || pbOpen ); assert( pPager->eState==PAGER_READER || !pbOpen ); assert( pbOpen==0 || *pbOpen==0 ); assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) ); if( !pPager->tempFile && !pPager->pWal ){ if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN; /* Close any rollback journal previously open */ sqlite3OsClose(pPager->jfd); rc = pagerOpenWal(pPager); if( rc==SQLITE_OK ){ pPager->journalMode = PAGER_JOURNALMODE_WAL; pPager->eState = PAGER_OPEN; } }else{ *pbOpen = 1; } return rc; } /* ** This function is called to close the connection to the log file prior ** to switching from WAL to rollback mode. ** ** Before closing the log file, this function attempts to take an ** EXCLUSIVE lock on the database file. If this cannot be obtained, an ** error (SQLITE_BUSY) is returned and the log connection is not closed. ** If successful, the EXCLUSIVE lock is not released before returning. */ int sqlite3PagerCloseWal(Pager *pPager, sqlite3 *db){ int rc = SQLITE_OK; assert( pPager->journalMode==PAGER_JOURNALMODE_WAL ); /* If the log file is not already open, but does exist in the file-system, ** it may need to be checkpointed before the connection can switch to ** rollback mode. Open it now so this can happen. */ if( !pPager->pWal ){ int logexists = 0; rc = pagerLockDb(pPager, SHARED_LOCK); if( rc==SQLITE_OK ){ rc = sqlite3OsAccess( pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists ); } if( rc==SQLITE_OK && logexists ){ rc = pagerOpenWal(pPager); } } /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on ** the database file, the log and log-summary files will be deleted. */ if( rc==SQLITE_OK && pPager->pWal ){ rc = pagerExclusiveLock(pPager); if( rc==SQLITE_OK ){ rc = sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags, pPager->pageSize, (u8*)pPager->pTmpSpace); pPager->pWal = 0; pagerFixMaplimit(pPager); if( rc && !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK); } } return rc; } #ifdef SQLITE_ENABLE_SETLK_TIMEOUT /* ** If pager pPager is a wal-mode database not in exclusive locking mode, ** invoke the sqlite3WalWriteLock() function on the associated Wal object ** with the same db and bLock parameters as were passed to this function. ** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise. */ int sqlite3PagerWalWriteLock(Pager *pPager, int bLock){ int rc = SQLITE_OK; if( pagerUseWal(pPager) && pPager->exclusiveMode==0 ){ rc = sqlite3WalWriteLock(pPager->pWal, bLock); } return rc; } /* ** Set the database handle used by the wal layer to determine if ** blocking locks are required. */ void sqlite3PagerWalDb(Pager *pPager, sqlite3 *db){ if( pagerUseWal(pPager) ){ sqlite3WalDb(pPager->pWal, db); } } #endif #ifdef SQLITE_ENABLE_SNAPSHOT /* ** If this is a WAL database, obtain a snapshot handle for the snapshot ** currently open. Otherwise, return an error. */ int sqlite3PagerSnapshotGet(Pager *pPager, sqlite3_snapshot **ppSnapshot){ int rc = SQLITE_ERROR; if( pPager->pWal ){ rc = sqlite3WalSnapshotGet(pPager->pWal, ppSnapshot); } return rc; } /* ** If this is a WAL database, store a pointer to pSnapshot. Next time a ** read transaction is opened, attempt to read from the snapshot it ** identifies. If this is not a WAL database, return an error. */ int sqlite3PagerSnapshotOpen( Pager *pPager, sqlite3_snapshot *pSnapshot ){ int rc = SQLITE_OK; if( pPager->pWal ){ sqlite3WalSnapshotOpen(pPager->pWal, pSnapshot); }else{ rc = SQLITE_ERROR; } return rc; } /* ** If this is a WAL database, call sqlite3WalSnapshotRecover(). If this ** is not a WAL database, return an error. */ int sqlite3PagerSnapshotRecover(Pager *pPager){ int rc; if( pPager->pWal ){ rc = sqlite3WalSnapshotRecover(pPager->pWal); }else{ rc = SQLITE_ERROR; } return rc; } /* ** The caller currently has a read transaction open on the database. ** If this is not a WAL database, SQLITE_ERROR is returned. Otherwise, ** this function takes a SHARED lock on the CHECKPOINTER slot and then ** checks if the snapshot passed as the second argument is still ** available. If so, SQLITE_OK is returned. ** ** If the snapshot is not available, SQLITE_ERROR is returned. Or, if ** the CHECKPOINTER lock cannot be obtained, SQLITE_BUSY. If any error ** occurs (any value other than SQLITE_OK is returned), the CHECKPOINTER ** lock is released before returning. */ int sqlite3PagerSnapshotCheck(Pager *pPager, sqlite3_snapshot *pSnapshot){ int rc; if( pPager->pWal ){ rc = sqlite3WalSnapshotCheck(pPager->pWal, pSnapshot); }else{ rc = SQLITE_ERROR; } return rc; } /* ** Release a lock obtained by an earlier successful call to ** sqlite3PagerSnapshotCheck(). */ void sqlite3PagerSnapshotUnlock(Pager *pPager){ assert( pPager->pWal ); sqlite3WalSnapshotUnlock(pPager->pWal); } #endif /* SQLITE_ENABLE_SNAPSHOT */ #endif /* !SQLITE_OMIT_WAL */ #ifdef SQLITE_ENABLE_ZIPVFS /* ** A read-lock must be held on the pager when this function is called. If ** the pager is in WAL mode and the WAL file currently contains one or more ** frames, return the size in bytes of the page images stored within the ** WAL frames. Otherwise, if this is not a WAL database or the WAL file ** is empty, return 0. */ int sqlite3PagerWalFramesize(Pager *pPager){ assert( pPager->eState>=PAGER_READER ); return sqlite3WalFramesize(pPager->pWal); } #endif #endif /* SQLITE_OMIT_DISKIO */