Change Win32 O_SYNC method to O_DSYNC because that is what the method

currently does.  This is now the default Win32 wal sync method because
we perfer o_datasync to fsync.

Also, change Win32 fsync to a new wal sync method called
fsync_writethrough because that is the behavior of _commit, which is
what is used for fsync on Win32.

Backpatch to 8.0.X.

doc/src/sgml/runtime.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.310 2005/03/19 23:27:04 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.311 2005/03/24 04:36:17 momjian Exp $
 -->
 
 <chapter Id="runtime">
@@ -1587,6 +1587,7 @@ SET ENABLE_SEQSCAN TO OFF;
         values are
         <literal>fsync</> (call <function>fsync()</> at each commit),
         <literal>fdatasync</> (call <function>fdatasync()</> at each commit),
+        <literal>fsync_writethrough</> (call <function>_commit()</> at each commit on Windows),
         <literal>open_sync</> (write WAL files with <function>open()</> option <symbol>O_SYNC</>), and
         <literal>open_datasync</> (write WAL files with <function>open()</> option <symbol>O_DSYNC</>).
         Not all of these choices are available on all platforms.

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.181 2005/02/12 23:53:37 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.182 2005/03/24 04:36:17 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -63,8 +63,13 @@
 #endif
 #endif
 
+#if defined(O_DSYNC)
 #if defined(OPEN_SYNC_FLAG)
-#if defined(O_DSYNC) && (O_DSYNC != OPEN_SYNC_FLAG)
+#if O_DSYNC != OPEN_SYNC_FLAG
+#define OPEN_DATASYNC_FLAG	  O_DSYNC
+#endif
+#else /* !defined(OPEN_SYNC_FLAG) */
+/* Win32 only has O_DSYNC */
 #define OPEN_DATASYNC_FLAG	  O_DSYNC
 #endif
 #endif
@@ -79,7 +84,11 @@
 #define DEFAULT_SYNC_METHOD		  SYNC_METHOD_FDATASYNC
 #define DEFAULT_SYNC_FLAGBIT	  0
 #else
+#ifndef FSYNC_IS_WRITE_THROUGH
 #define DEFAULT_SYNC_METHOD_STR   "fsync"
+#else
+#define DEFAULT_SYNC_METHOD_STR   "fsync_writethrough"
+#endif
 #define DEFAULT_SYNC_METHOD		  SYNC_METHOD_FSYNC
 #define DEFAULT_SYNC_FLAGBIT	  0
 #endif
@@ -5154,7 +5163,12 @@ assign_xlog_sync_method(const char *method, bool doit, GucSource source)
 	int			new_sync_method;
 	int			new_sync_bit;
 
+#ifndef FSYNC_IS_WRITE_THROUGH
 	if (pg_strcasecmp(method, "fsync") == 0)
+#else
+	/* Win32 fsync() == _commit(0, which writes through a write cache */
+	if (pg_strcasecmp(method, "fsync_writethrough") == 0)
+#endif
 	{
 		new_sync_method = SYNC_METHOD_FSYNC;
 		new_sync_bit = 0;

src/backend/utils/misc/postgresql.conf.sample

@@ -114,7 +114,8 @@
 
 #fsync = true			# turns forced synchronization on or off
 #wal_sync_method = fsync	# the default varies across platforms:
-				# fsync, fdatasync, open_sync, or open_datasync
+				# fsync, fdatasync, fsync_writethrough,
+				# open_sync, open_datasync
 #wal_buffers = 8		# min 4, 8KB each
 #commit_delay = 0		# range 0-100000, in microseconds
 #commit_siblings = 5		# range 1-1000

src/include/port/win32.h

-/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.43 2005/02/27 00:53:29 momjian Exp $ */
+/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.44 2005/03/24 04:36:19 momjian Exp $ */
 
 /* undefine and redefine after #include */
 #undef mkdir
@@ -17,6 +17,7 @@
 
 
 #define fsync(a)	_commit(a)
+#define FSYNC_IS_WRITE_THROUGH
 #define ftruncate(a,b)	chsize(a,b)
 
 #define USES_WINSOCK
@@ -189,7 +190,7 @@ typedef int pid_t;
  * to ensure that we don't collide with a future definition. It means
  * we cannot use _O_NOINHERIT ourselves.
  */
-#define O_SYNC 0x0080
+#define O_DSYNC 0x0080
 
 /*
  * Supplement to <errno.h>.

src/port/open.c

@@ -6,7 +6,7 @@
  *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/port/open.c,v 1.8 2005/02/27 00:53:29 momjian Exp $
+ * $PostgreSQL: pgsql/src/port/open.c,v 1.9 2005/03/24 04:36:20 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -63,7 +63,7 @@ win32_open(const char *fileName, int fileFlags,...)
 	/* Check that we can handle the request */
 	assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
 						 (O_RANDOM | O_SEQUENTIAL | O_TEMPORARY) |
-						 _O_SHORT_LIVED | O_SYNC |
+						 _O_SHORT_LIVED | O_DSYNC |
 	  (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
 
 	sa.nLength = sizeof(sa);
@@ -83,7 +83,7 @@ win32_open(const char *fileName, int fileFlags,...)
 		   ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
 		  ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
 			 ((fileFlags & O_TEMPORARY) ? FILE_FLAG_DELETE_ON_CLOSE : 0)|
-					((fileFlags & O_SYNC) ? FILE_FLAG_WRITE_THROUGH : 0),
+					((fileFlags & O_DSYNC) ? FILE_FLAG_WRITE_THROUGH : 0),
 						NULL)) == INVALID_HANDLE_VALUE)
 	{
 		switch (GetLastError())