From 42bd2d6c0ff4cd931ec3d4008438842bab5acd4b Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Fri, 26 Aug 2022 14:27:43 +1200
Subject: [PATCH 1/3] Remove wal_sync_method=fsync_writethrough on Windows.

The fsync and fdatasync levels already flush drive write caches on
Windows, so it only confuses matters to have an apparently higher level
that isn't actually higher.  We don't do that on any other OS.
---
 doc/src/sgml/wal.sgml                 | 5 ++---
 src/backend/storage/file/fd.c         | 6 ++----
 src/bin/pg_test_fsync/pg_test_fsync.c | 4 +---
 src/include/port/win32_port.h         | 8 --------
 4 files changed, 5 insertions(+), 18 deletions(-)

diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 01f7379ebb..90cbacfe41 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -108,9 +108,8 @@
         <literal>open_datasync</literal> (the default), write caching can be disabled
         by unchecking <literal>My Computer\Open\<replaceable>disk drive</replaceable>\Properties\Hardware\Properties\Policies\Enable write caching on the disk</literal>.
         Alternatively, set <varname>wal_sync_method</varname> to
-        <literal>fdatasync</literal> (NTFS only), <literal>fsync</literal> or
-        <literal>fsync_writethrough</literal>, which prevent
-        write caching.
+        <literal>fdatasync</literal> (NTFS only) or <literal>fsync</literal>,
+        which prevent write caching.
       </para>
     </listitem>
 
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index e3b19ca1ed..c27a6600fe 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -395,7 +395,7 @@ pg_fsync(int fd)
 #endif
 
 	/* #if is to skip the sync_method test if there's no need for it */
-#if defined(HAVE_FSYNC_WRITETHROUGH) && !defined(FSYNC_WRITETHROUGH_IS_FSYNC)
+#if defined(HAVE_FSYNC_WRITETHROUGH)
 	if (sync_method == SYNC_METHOD_FSYNC_WRITETHROUGH)
 		return pg_fsync_writethrough(fd);
 	else
@@ -425,9 +425,7 @@ pg_fsync_writethrough(int fd)
 {
 	if (enableFsync)
 	{
-#ifdef WIN32
-		return _commit(fd);
-#elif defined(F_FULLFSYNC)
+#if defined(F_FULLFSYNC)
 		return (fcntl(fd, F_FULLFSYNC, 0) == -1) ? -1 : 0;
 #else
 		errno = ENOSYS;
diff --git a/src/bin/pg_test_fsync/pg_test_fsync.c b/src/bin/pg_test_fsync/pg_test_fsync.c
index 77f0db0376..e23e2601ad 100644
--- a/src/bin/pg_test_fsync/pg_test_fsync.c
+++ b/src/bin/pg_test_fsync/pg_test_fsync.c
@@ -605,9 +605,7 @@ signal_cleanup(int signum)
 static int
 pg_fsync_writethrough(int fd)
 {
-#ifdef WIN32
-	return _commit(fd);
-#elif defined(F_FULLFSYNC)
+#if defined(F_FULLFSYNC)
 	return (fcntl(fd, F_FULLFSYNC, 0) == -1) ? -1 : 0;
 #else
 	errno = ENOSYS;
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index 707f8760ca..b6769a1693 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -75,14 +75,6 @@
 /* Windows doesn't have fsync() as such, use _commit() */
 #define fsync(fd) _commit(fd)
 
-/*
- * For historical reasons, we allow setting wal_sync_method to
- * fsync_writethrough on Windows, even though it's really identical to fsync
- * (both code paths wind up at _commit()).
- */
-#define HAVE_FSYNC_WRITETHROUGH
-#define FSYNC_WRITETHROUGH_IS_FSYNC
-
 #define USES_WINSOCK
 
 /*
-- 
2.35.1