Summary:
This patch allows rocksdb to persist options into a file on
DB::Open, SetOptions, and Create / Drop ColumnFamily.
Options files are created under the same directory as the rocksdb
instance.

In addition, this patch also adds a fail_if_missing_options_file in DBOptions
that makes any function call return non-ok status when it is not able to
persist options properly.

  // If true, then DB::Open / CreateColumnFamily / DropColumnFamily
  // / SetOptions will fail if options file is not detected or properly
  // persisted.
  //
  // DEFAULT: false
  bool fail_if_missing_options_file;

Options file names are formatted as OPTIONS-<number>, and RocksDB
will always keep the latest two options files.

Test Plan:
Add options_file_test.

options_test
column_family_test

Reviewers: igor, IslamAbdelRahman, sdong, anthony

Reviewed By: anthony

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D48285

Summary:
Using a TLS random instance for skiplist makes it smaller
(useful for hash_skiplist_rep) and prepares skiplist for concurrent
adds.  This diff also modifies the branching factor math to avoid an
unnecessary division.

This diff has the effect of changing the sequence of skip list node
height choices made by tests, so it has the potential to cause unit
test failures for tests that implicitly rely on the exact structure
of the skip list.  Tests that try to exactly trigger a compaction are
likely suspects for this problem (these tests have always been brittle to
changes in the skiplist details).  I've minimizes this risk by reseeding
the main thread's Random at the beginning of each test, increasing the
universal compaction size_ratio limit from 101% to 105% for some tests,
and verifying that the tests pass many times.

Test Plan: for i in `seq 0 9`; do make check; done

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D50439

Signed-off-by: NSage Weil <sage@redhat.com>

Summary:
This diff exclude alot of tests in db_test that are not compiling / failing under ROCKSD_LITE

Test Plan:
OPT=-DROCKSDB_LITE make check -j64
make check -j64

Reviewers: yhchiang, igor, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D48771

Summary: db_test_util is used in multiple test files but it dont compile under ROCKSDB_LITE

Test Plan:
make check
make static_lib
OPT=-DROCKSDB_LITE make db_wal_test

Reviewers: igor, yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D48579

Summary:
Separate a new class InternalIterator from class Iterator, when the look-up is done internally, which also means they operate on key with sequence ID and type.

This change will enable potential future optimizations but for now InternalIterator's functions are still the same as Iterator's.
At the same time, separate the cleanup function to a separate class and let both of InternalIterator and Iterator inherit from it.

Test Plan: Run all existing tests.

Reviewers: igor, yhchiang, anthony, kradhakrishnan, IslamAbdelRahman, rven

Reviewed By: rven

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D48549

Summary:
Long time ago we add InternalDumpCommand to ldb_tool https://reviews.facebook.net/D11517
This command is using TEST_NewInternalIterator although it's not a test. This patch move TEST_NewInternalIterator outside of db_impl_debug.cc

Test Plan:
make check
make static_lib

Reviewers: yhchiang, igor, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D48561

Summary:
As part of tech debt week, we are cleaning up dependencies.
This diff moves db_test_util.[h,cc] from util to db directory.

Test Plan: make check

Reviewers: igor, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D48543

Summary:
	Handle SST files with both ".sst" and ".ldb" suffix.
	This enables user to migrate from leveldb to rocksdb.

Test Plan:
        Added unit test with DB operating on SSTs with names schema.
        See db/dc_test.cc:SSTsWithLdbSuffixHandling for details

Reviewers: yhchiang, sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D48003

Summary:
PlainTableReader now only allows mmap-mode. Add the support to non-mmap mode for more flexibility.
Refactor the codes to move all logic of reading data to PlainTableKeyDecoder, and consolidate the calls to Read() call and ReadVarint32() call. Implement the calls for both of mmap and non-mmap case seperately. For non-mmap mode, make copy of keys in several places when we need to move the buffer after reading the keys.

Test Plan: Add the mode of non-mmap case in plain_table_db_test. Run it in valgrind mode too.

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D47187

Summary:
This patch fixes #7460559. It introduces SingleDelete as a new database
operation. This operation can be used to delete keys that were never
overwritten (no put following another put of the same key). If an overwritten
key is single deleted the behavior is undefined. Single deletion of a
non-existent key has no effect but multiple consecutive single deletions are
not allowed (see limitations).

In contrast to the conventional Delete() operation, the deletion entry is
removed along with the value when the two are lined up in a compaction. Note:
The semantics are similar to @igor's prototype that allowed to have this
behavior on the granularity of a column family (
https://reviews.facebook.net/D42093 ). This new patch, however, is more
aggressive when it comes to removing tombstones: It removes the SingleDelete
together with the value whenever there is no snapshot between them while the
older patch only did this when the sequence number of the deletion was older
than the earliest snapshot.

Most of the complex additions are in the Compaction Iterator, all other changes
should be relatively straightforward. The patch also includes basic support for
single deletions in db_stress and db_bench.

Limitations:
- Not compatible with cuckoo hash tables
- Single deletions cannot be used in combination with merges and normal
  deletions on the same key (other keys are not affected by this)
- Consecutive single deletions are currently not allowed (and older version of
  this patch supported this so it could be resurrected if needed)

Test Plan: make all check

Reviewers: yhchiang, sdong, rven, anthony, yoshinorim, igor

Reviewed By: igor

Subscribers: maykov, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D43179

Summary:
In some cases, equality comparisons can be done more efficiently than three-way
comparisons. There are quite a few places in the code where we only care about
equality. This patch adds an Equal() method that defaults to using the
Compare() method.

Test Plan: make clean all check

Reviewers: rven, anthony, yhchiang, igor, sdong

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D46233

Summary:
Now that the approach to parallelizing L0-L1 level-based
compactions by breaking the compaction job into subcompactions is
being extended to apply to universal compactions as well, the unit
tests need to account for this and run the universal compaction
tests with subcompactions both enabled and disabled.

Test Plan: make all && make check

Reviewers: sdong, igor, noetzli, anthony, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D45657

Summary: malloc_usable_size() gets a better estimation of memory usage. It is already used to calculate block cache memory usage. Use it in arena too.

Test Plan: Run all unit tests

Reviewers: anthony, kradhakrishnan, rven, IslamAbdelRahman, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D43317

Summary:
ReadaheadRandomAccessFile acts as a transparent layer on top of RandomAccessFile. When a Read() request is issued, it issues a much bigger request to the OS and caches the result. When a new request comes in and we already have the data cached, it doesn't have to issue any requests to the OS.

We add ReadaheadRandomAccessFile layer only when file is read during compactions.

D45105 was incorrectly closed by Phabricator because I committed it to a separate branch (not master), so I'm resubmitting the diff.

Test Plan: make check

Reviewers: MarkCallaghan, sdong

Reviewed By: sdong

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D45123

Summary:
See task #7983654. The example was triggering an assert in compaction job
because the compaction was not marked as manual. With this patch,
CompactionPicker::FormCompaction() marks compactions as manual. This patch
also fixes a couple of typos, adds optimistic_transaction_example to
.gitignore and librocksdb as a dependency for examples. Adding librocksdb as
a dependency makes sure that the examples are built with the latest changes
in librocksdb.

Test Plan: make clean && cd examples && make all && ./compact_files_example

Reviewers: rven, sdong, anthony, igor, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D45117

Summary:
Up until this point we had DbOptions.num_subcompactions, but
it is semantically more correct to call this max_subcompactions since
we will schedule *up to* DbOptions.max_subcompactions smaller compactions
at a time during a compaction job.

I also added a --subcompactions option to db_bench

Test Plan: make all   make check

Reviewers: sdong, igor, anthony, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D45069

Summary: Currently compaction inputs share the same file descriptor and table reader as other foreground threads. It makes fadvise works less predictable. Add options.new_table_reader_for_compaction_inputs to enforce to create a new file descriptor and new table reader for it.

Test Plan: Add the option.

Reviewers: rven, anthony, kradhakrishnan, IslamAbdelRahman, igor, yhchiang

Reviewed By: igor

Subscribers: igor, MarkCallaghan, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D43311

Summary:
Updated DBTest DBCompactionTest and CompactionJobStatsTest
to run compaction-related tests once with subcompactions enabled and
once disabled using the TEST_P test type in the Google Test suite.

Test Plan: ./db_test  ./db_compaction-test  ./compaction_job_stats_test

Reviewers: sdong, igor, anthony, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D43443

Summary:
UpdateAccumulatedStats() is used to optimize compaction decision
esp. when the number of deletion entries are high, but this function
can slowdown DBOpen esp. in disk environment.

This patch adds DBOptions::skip_sats_update_on_db_open, which skips
UpdateAccumulatedStats() in DB::Open() time when it's set to true.

Test Plan: Add DBCompactionTest.SkipStatsUpdateTest

Reviewers: igor, anthony, IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: tnovak, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42843

Summary:
As of now compactions involving files from Level 0 and Level 1 are single
threaded because the files in L0, although sorted, are not range partitioned like
the other levels. This means that during L0-L1 compaction each file from L1
needs to be merged with potentially all the files from L0.

This attempt to parallelize the L0-L1 compaction assigns a thread and a
corresponding iterator to each L1 file that then considers only the key range
found in that L1 file and only the L0 files that have those keys (and only the
specific portion of those L0 files in which those keys are found). In this way
the overlap is minimized and potentially eliminated between different iterators
focusing on the same files.

The first step is to restructure the compaction logic to break L0-L1 compactions
into multiple, smaller, sequential compactions. Eventually each of these smaller
jobs will be run simultaneously. Areas to pay extra attention to are

  # Correct aggregation of compaction job statistics across multiple threads
  # Proper opening/closing of output files (make sure each thread's is unique)
  # Keys that span multiple L1 files
  # Skewed distributions of keys within L0 files

Test Plan: Make and run db_test (newer version has separate compaction tests) and compaction_job_stats_test

Reviewers: igor, noetzli, anthony, sdong, yhchiang

Reviewed By: yhchiang

Subscribers: MarkCallaghan, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42699

Summary: Directly using TMPDIR can cause problems when running tests using parallel option. Fix them.

Test Plan: Run all tests in parallel

Reviewers: kradhakrishnan, yhchiang, IslamAbdelRahman, anthony

Reviewed By: anthony

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D42807

Summary:
When we first started, max_background_flushes was 0 by default and compaction thread was executing flushes (since there was no flush thread). Then, we switched the default max_background_flushes to 1. However, we still support the case where there is no flush thread and flushes are done in compaction. This is making our code a bit more complicated. By not supporting this use-case we can make our code simpler.

We have a special case that when you set max_background_flushes to 0, we
schedule the flush to execute on the compaction thread.

Test Plan: make check (there might be some unit tests that depend on this behavior)

Reviewers: IslamAbdelRahman, yhchiang, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41931

Summary:
Trvial move in universal compaction was failing when trying to move files from levels other than 0.
This was because the DeleteFile while trivially moving, was only deleting files of level 0 which caused duplication of same file in different levels.
This is fixed by passing the right level as argument in the call of DeleteFile while doing trivial move.

Test Plan: ./db_test ran successfully with the new test cases.

Reviewers: sdong

Reviewed By: sdong

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D42135

Summary: Make TransactionLogIterator related tests from db_test.cc to db_log_iter_test.cc

Test Plan:
db_test
db_log_iter_test

Reviewers: sdong, IslamAbdelRahman, igor, anthony

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42045

Summary: Block SyncPoint in util/db_test_util.h in released Windows mode.

Test Plan: db_test

Reviewers: igor, anthony, sdong, IslamAbdelRahman

Reviewed By: sdong, IslamAbdelRahman

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42213

Summary: This option is guarding the feature implemented 2 and a half years ago: D8991. The feature was enabled by default back then and has been running without issues. There is no reason why any client would turn this feature off. I found no reference in fbcode.

Test Plan: none

Reviewers: sdong, yhchiang, anthony, dhruba

Reviewed By: dhruba

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42063

Summary:
Move reusable part of db_test.cc to util/db_test_util.h.
This makes it more possible to partition db_test.cc into
multiple smaller test files.

Also, fixed many old lint errors in db_test.

Test Plan: db_test

Reviewers: igor, anthony, IslamAbdelRahman, sdong, kradhakrishnan

Reviewed By: sdong, kradhakrishnan

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41973