Improve the naming in wal_sync_method code.

* sync_method is renamed to wal_sync_method.

* sync_method_options[] is renamed to wal_sync_method_options[].

* assign_xlog_sync_method() is renamed to assign_wal_sync_method().

* The names of the available synchronization methods are now
  prefixed with "WAL_SYNC_METHOD_" and have been moved into a
  WalSyncMethod enum.

* PLATFORM_DEFAULT_SYNC_METHOD is renamed to
  PLATFORM_DEFAULT_WAL_SYNC_METHOD, and DEFAULT_SYNC_METHOD is
  renamed to DEFAULT_WAL_SYNC_METHOD.

These more descriptive names help distinguish the code for
wal_sync_method from the code for DataDirSyncMethod (e.g., the
recovery_init_sync_method configuration parameter and the
--sync-method option provided by several frontend utilities).  This
change also prevents name collisions between the aforementioned
sets of code.  Since this only improves the naming of internal
identifiers, there should be no behavior change.

Author: Maxim Orlov
Discussion: https://postgr.es/m/CACG%3DezbL1gwE7_K7sr9uqaCGkWhmvRTcTEnm3%2BX1xsRNwbXULQ%40mail.gmail.com

src/backend/access/transam/xlog.c

@@ -130,7 +130,7 @@ bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
 bool		wal_recycle = true;
 bool		log_checkpoints = true;
-int			sync_method = DEFAULT_SYNC_METHOD;
+int			wal_sync_method = DEFAULT_WAL_SYNC_METHOD;
 int			wal_level = WAL_LEVEL_REPLICA;
 int			CommitDelay = 0;	/* precommit delay in microseconds */
 int			CommitSiblings = 5; /* # concurrent xacts needed to sleep */
@@ -171,17 +171,17 @@ static bool check_wal_consistency_checking_deferred = false;
 /*
  * GUC support
  */
-const struct config_enum_entry sync_method_options[] = {
-	{"fsync", SYNC_METHOD_FSYNC, false},
+const struct config_enum_entry wal_sync_method_options[] = {
+	{"fsync", WAL_SYNC_METHOD_FSYNC, false},
 #ifdef HAVE_FSYNC_WRITETHROUGH
-	{"fsync_writethrough", SYNC_METHOD_FSYNC_WRITETHROUGH, false},
+	{"fsync_writethrough", WAL_SYNC_METHOD_FSYNC_WRITETHROUGH, false},
 #endif
-	{"fdatasync", SYNC_METHOD_FDATASYNC, false},
+	{"fdatasync", WAL_SYNC_METHOD_FDATASYNC, false},
 #ifdef O_SYNC
-	{"open_sync", SYNC_METHOD_OPEN, false},
+	{"open_sync", WAL_SYNC_METHOD_OPEN, false},
 #endif
 #ifdef O_DSYNC
-	{"open_datasync", SYNC_METHOD_OPEN_DSYNC, false},
+	{"open_datasync", WAL_SYNC_METHOD_OPEN_DSYNC, false},
 #endif
 	{NULL, 0, false}
 };
@@ -2343,8 +2343,8 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible)
 		 * have no open file or the wrong one.  However, we do not need to
 		 * fsync more than one file.
 		 */
-		if (sync_method != SYNC_METHOD_OPEN &&
-			sync_method != SYNC_METHOD_OPEN_DSYNC)
+		if (wal_sync_method != WAL_SYNC_METHOD_OPEN &&
+			wal_sync_method != WAL_SYNC_METHOD_OPEN_DSYNC)
 		{
 			if (openLogFile >= 0 &&
 				!XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo,
@@ -2974,7 +2974,7 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli,
 	 */
 	*added = false;
 	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | O_CLOEXEC |
-					   get_sync_bit(sync_method));
+					   get_sync_bit(wal_sync_method));
 	if (fd < 0)
 	{
 		if (errno != ENOENT)
@@ -3139,7 +3139,7 @@ XLogFileInit(XLogSegNo logsegno, TimeLineID logtli)
 
 	/* Now open original target segment (might not be file I just made) */
 	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | O_CLOEXEC |
-					   get_sync_bit(sync_method));
+					   get_sync_bit(wal_sync_method));
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -3371,7 +3371,7 @@ XLogFileOpen(XLogSegNo segno, TimeLineID tli)
 	XLogFilePath(path, tli, segno, wal_segment_size);
 
 	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | O_CLOEXEC |
-					   get_sync_bit(sync_method));
+					   get_sync_bit(wal_sync_method));
 	if (fd < 0)
 		ereport(PANIC,
 				(errcode_for_file_access(),
@@ -8137,16 +8137,16 @@ get_sync_bit(int method)
 			 * not included in the enum option array, and therefore will never
 			 * be seen here.
 			 */
-		case SYNC_METHOD_FSYNC:
-		case SYNC_METHOD_FSYNC_WRITETHROUGH:
-		case SYNC_METHOD_FDATASYNC:
+		case WAL_SYNC_METHOD_FSYNC:
+		case WAL_SYNC_METHOD_FSYNC_WRITETHROUGH:
+		case WAL_SYNC_METHOD_FDATASYNC:
 			return o_direct_flag;
 #ifdef O_SYNC
-		case SYNC_METHOD_OPEN:
+		case WAL_SYNC_METHOD_OPEN:
 			return O_SYNC | o_direct_flag;
 #endif
 #ifdef O_DSYNC
-		case SYNC_METHOD_OPEN_DSYNC:
+		case WAL_SYNC_METHOD_OPEN_DSYNC:
 			return O_DSYNC | o_direct_flag;
 #endif
 		default:
@@ -8160,9 +8160,9 @@ get_sync_bit(int method)
  * GUC support
  */
 void
-assign_xlog_sync_method(int new_sync_method, void *extra)
+assign_wal_sync_method(int new_wal_sync_method, void *extra)
 {
-	if (sync_method != new_sync_method)
+	if (wal_sync_method != new_wal_sync_method)
 	{
 		/*
 		 * To ensure that no blocks escape unsynced, force an fsync on the
@@ -8188,7 +8188,7 @@ assign_xlog_sync_method(int new_sync_method, void *extra)
 			}
 
 			pgstat_report_wait_end();
-			if (get_sync_bit(sync_method) != get_sync_bit(new_sync_method))
+			if (get_sync_bit(wal_sync_method) != get_sync_bit(new_wal_sync_method))
 				XLogFileClose();
 		}
 	}
@@ -8214,8 +8214,8 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
 	 * file.
 	 */
 	if (!enableFsync ||
-		sync_method == SYNC_METHOD_OPEN ||
-		sync_method == SYNC_METHOD_OPEN_DSYNC)
+		wal_sync_method == WAL_SYNC_METHOD_OPEN ||
+		wal_sync_method == WAL_SYNC_METHOD_OPEN_DSYNC)
 		return;
 
 	/* Measure I/O timing to sync the WAL file */
@@ -8225,29 +8225,29 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
 		INSTR_TIME_SET_ZERO(start);
 
 	pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC);
-	switch (sync_method)
+	switch (wal_sync_method)
 	{
-		case SYNC_METHOD_FSYNC:
+		case WAL_SYNC_METHOD_FSYNC:
 			if (pg_fsync_no_writethrough(fd) != 0)
 				msg = _("could not fsync file \"%s\": %m");
 			break;
 #ifdef HAVE_FSYNC_WRITETHROUGH
-		case SYNC_METHOD_FSYNC_WRITETHROUGH:
+		case WAL_SYNC_METHOD_FSYNC_WRITETHROUGH:
 			if (pg_fsync_writethrough(fd) != 0)
 				msg = _("could not fsync write-through file \"%s\": %m");
 			break;
 #endif
-		case SYNC_METHOD_FDATASYNC:
+		case WAL_SYNC_METHOD_FDATASYNC:
 			if (pg_fdatasync(fd) != 0)
 				msg = _("could not fdatasync file \"%s\": %m");
 			break;
-		case SYNC_METHOD_OPEN:
-		case SYNC_METHOD_OPEN_DSYNC:
+		case WAL_SYNC_METHOD_OPEN:
+		case WAL_SYNC_METHOD_OPEN_DSYNC:
 			/* not reachable */
 			Assert(false);
 			break;
 		default:
-			elog(PANIC, "unrecognized wal_sync_method: %d", sync_method);
+			elog(PANIC, "unrecognized wal_sync_method: %d", wal_sync_method);
 			break;
 	}
 

src/backend/storage/file/fd.c

@@ -398,9 +398,9 @@ pg_fsync(int fd)
 	errno = 0;
 #endif
 
-	/* #if is to skip the sync_method test if there's no need for it */
+	/* #if is to skip the wal_sync_method test if there's no need for it */
 #if defined(HAVE_FSYNC_WRITETHROUGH)
-	if (sync_method == SYNC_METHOD_FSYNC_WRITETHROUGH)
+	if (wal_sync_method == WAL_SYNC_METHOD_FSYNC_WRITETHROUGH)
 		return pg_fsync_writethrough(fd);
 	else
 #endif

src/backend/utils/misc/guc_tables.c

@@ -485,7 +485,7 @@ static const struct config_enum_entry wal_compression_options[] = {
 extern const struct config_enum_entry wal_level_options[];
 extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
-extern const struct config_enum_entry sync_method_options[];
+extern const struct config_enum_entry wal_sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
 
 /*
@@ -4843,9 +4843,9 @@ struct config_enum ConfigureNamesEnum[] =
 			gettext_noop("Selects the method used for forcing WAL updates to disk."),
 			NULL
 		},
-		&sync_method,
-		DEFAULT_SYNC_METHOD, sync_method_options,
-		NULL, assign_xlog_sync_method, NULL
+		&wal_sync_method,
+		DEFAULT_WAL_SYNC_METHOD, wal_sync_method_options,
+		NULL, assign_wal_sync_method, NULL
 	},
 
 	{

src/include/access/xlog.h

@@ -19,12 +19,15 @@
 
 
 /* Sync methods */
-#define SYNC_METHOD_FSYNC		0
-#define SYNC_METHOD_FDATASYNC	1
-#define SYNC_METHOD_OPEN		2	/* for O_SYNC */
-#define SYNC_METHOD_FSYNC_WRITETHROUGH	3
-#define SYNC_METHOD_OPEN_DSYNC	4	/* for O_DSYNC */
-extern PGDLLIMPORT int sync_method;
+typedef enum WalSyncMethod
+{
+	WAL_SYNC_METHOD_FSYNC = 0,
+	WAL_SYNC_METHOD_FDATASYNC,
+	WAL_SYNC_METHOD_OPEN,		/* for O_SYNC */
+	WAL_SYNC_METHOD_FSYNC_WRITETHROUGH,
+	WAL_SYNC_METHOD_OPEN_DSYNC	/* for O_DSYNC */
+} WalSyncMethod;
+extern PGDLLIMPORT int wal_sync_method;
 
 extern PGDLLIMPORT XLogRecPtr ProcLastRecPtr;
 extern PGDLLIMPORT XLogRecPtr XactLastRecEnd;

src/include/access/xlogdefs.h

@@ -71,12 +71,12 @@ typedef uint16 RepOriginId;
  *
  * Note that we define our own O_DSYNC on Windows, but not O_SYNC.
  */
-#if defined(PLATFORM_DEFAULT_SYNC_METHOD)
-#define DEFAULT_SYNC_METHOD		PLATFORM_DEFAULT_SYNC_METHOD
+#if defined(PLATFORM_DEFAULT_WAL_SYNC_METHOD)
+#define DEFAULT_WAL_SYNC_METHOD		PLATFORM_DEFAULT_WAL_SYNC_METHOD
 #elif defined(O_DSYNC) && (!defined(O_SYNC) || O_DSYNC != O_SYNC)
-#define DEFAULT_SYNC_METHOD		SYNC_METHOD_OPEN_DSYNC
+#define DEFAULT_WAL_SYNC_METHOD		WAL_SYNC_METHOD_OPEN_DSYNC
 #else
-#define DEFAULT_SYNC_METHOD		SYNC_METHOD_FDATASYNC
+#define DEFAULT_WAL_SYNC_METHOD		WAL_SYNC_METHOD_FDATASYNC
 #endif
 
 #endif							/* XLOG_DEFS_H */

src/include/port/freebsd.h

@@ -5,4 +5,4 @@
  * would prefer open_datasync on FreeBSD 13+, but that is not a good choice on
  * many systems.
  */
-#define PLATFORM_DEFAULT_SYNC_METHOD	SYNC_METHOD_FDATASYNC
+#define PLATFORM_DEFAULT_WAL_SYNC_METHOD	WAL_SYNC_METHOD_FDATASYNC

src/include/port/linux.h

@@ -19,4 +19,4 @@
  * perform better and (b) causes outright failures on ext4 data=journal
  * filesystems, because those don't support O_DIRECT.
  */
-#define PLATFORM_DEFAULT_SYNC_METHOD	SYNC_METHOD_FDATASYNC
+#define PLATFORM_DEFAULT_WAL_SYNC_METHOD	WAL_SYNC_METHOD_FDATASYNC

src/include/utils/guc_hooks.h

@@ -159,6 +159,6 @@ extern bool check_wal_consistency_checking(char **newval, void **extra,
 										   GucSource source);
 extern void assign_wal_consistency_checking(const char *newval, void *extra);
 extern bool check_wal_segment_size(int *newval, void **extra, GucSource source);
-extern void assign_xlog_sync_method(int new_sync_method, void *extra);
+extern void assign_wal_sync_method(int new_wal_sync_method, void *extra);
 
 #endif							/* GUC_HOOKS_H */

src/tools/pgindent/typedefs.list

@@ -3016,6 +3016,7 @@ WalSnd
 WalSndCtlData
 WalSndSendDataCallback
 WalSndState
+WalSyncMethod
 WalTimeSample
 WalUsage
 WalWriteMethod