Merge wal_level "archive" and "hot_standby" into new name "replica"

The distinction between "archive" and "hot_standby" existed only because
at the time "hot_standby" was added, there was some uncertainty about
stability.  This is now a long time ago.  We would like to move forward
with simplifying the replication configuration, but this distinction is
in the way, because a primary server cannot tell (without asking a
standby or predicting the future) which one of these would be the
appropriate level.

Pick a new name for the combined setting to make it clearer that it
covers all (non-logical) backup and replication uses.  The old values
are still accepted but are converted internally.

Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: David Steele <david@pgmasters.net>

src/backend/access/rmgrdesc/xlogdesc.c

@@ -25,8 +25,9 @@
  */
 const struct config_enum_entry wal_level_options[] = {
 	{"minimal", WAL_LEVEL_MINIMAL, false},
-	{"archive", WAL_LEVEL_ARCHIVE, false},
-	{"hot_standby", WAL_LEVEL_HOT_STANDBY, false},
+	{"replica", WAL_LEVEL_REPLICA, false},
+	{"archive", WAL_LEVEL_REPLICA, true},  /* deprecated */
+	{"hot_standby", WAL_LEVEL_REPLICA, true},  /* deprecated */
 	{"logical", WAL_LEVEL_LOGICAL, false},
 	{NULL, 0, false}
 };

src/backend/access/transam/xact.c

@@ -1254,7 +1254,7 @@ RecordTransactionCommit(void)
 	 * this case, but we don't currently try to do that.  It would certainly
 	 * cause problems at least in Hot Standby mode, where the
 	 * KnownAssignedXids machinery requires tracking every XID assignment.  It
-	 * might be OK to skip it only when wal_level < hot_standby, but for now
+	 * might be OK to skip it only when wal_level < replica, but for now
 	 * we don't.)
 	 *
 	 * However, if we're doing cleanup of any non-temp rels or committing any

src/backend/access/transam/xlog.c

@@ -5866,7 +5866,7 @@ static void
 CheckRequiredParameterValues(void)
 {
 	/*
-	 * For archive recovery, the WAL must be generated with at least 'archive'
+	 * For archive recovery, the WAL must be generated with at least 'replica'
 	 * wal_level.
 	 */
 	if (ArchiveRecoveryRequested && ControlFile->wal_level == WAL_LEVEL_MINIMAL)
@@ -5877,15 +5877,15 @@ CheckRequiredParameterValues(void)
 	}
 
 	/*
-	 * For Hot Standby, the WAL must be generated with 'hot_standby' mode, and
+	 * For Hot Standby, the WAL must be generated with 'replica' mode, and
 	 * we must have at least as many backend slots as the primary.
 	 */
 	if (ArchiveRecoveryRequested && EnableHotStandby)
 	{
-		if (ControlFile->wal_level < WAL_LEVEL_HOT_STANDBY)
+		if (ControlFile->wal_level < WAL_LEVEL_REPLICA)
 			ereport(ERROR,
-					(errmsg("hot standby is not possible because wal_level was not set to \"hot_standby\" or higher on the master server"),
-					 errhint("Either set wal_level to \"hot_standby\" on the master, or turn off hot_standby here.")));
+					(errmsg("hot standby is not possible because wal_level was not set to \"replica\" or higher on the master server"),
+					 errhint("Either set wal_level to \"replica\" on the master, or turn off hot_standby here.")));
 
 		/* We ignore autovacuum_max_workers when we make this test. */
 		RecoveryRequiresIntParameter("max_connections",
@@ -9459,10 +9459,8 @@ xlog_redo(XLogReaderState *record)
 		/*
 		 * Update minRecoveryPoint to ensure that if recovery is aborted, we
 		 * recover back up to this point before allowing hot standby again.
-		 * This is particularly important if wal_level was set to 'archive'
-		 * before, and is now 'hot_standby', to ensure you don't run queries
-		 * against the WAL preceding the wal_level change. Same applies to
-		 * decreasing max_* settings.
+		 * This is important if the max_* settings are decreased, to ensure
+		 * you don't run queries against the WAL preceding the change.
 		 */
 		minRecoveryPoint = ControlFile->minRecoveryPoint;
 		minRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
@@ -9793,7 +9791,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
 		ereport(ERROR,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 			  errmsg("WAL level not sufficient for making an online backup"),
-				 errhint("wal_level must be set to \"archive\", \"hot_standby\", or \"logical\" at server start.")));
+				 errhint("wal_level must be set to \"replica\" or \"logical\" at server start.")));
 
 	if (strlen(backupidstr) > MAXPGPATH)
 		ereport(ERROR,
@@ -10264,7 +10262,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
 		ereport(ERROR,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 			  errmsg("WAL level not sufficient for making an online backup"),
-				 errhint("wal_level must be set to \"archive\", \"hot_standby\", or \"logical\" at server start.")));
+				 errhint("wal_level must be set to \"replica\" or \"logical\" at server start.")));
 
 	/*
 	 * OK to update backup counters and forcePageWrites

src/backend/access/transam/xlogfuncs.c

@@ -154,7 +154,7 @@ pg_create_restore_point(PG_FUNCTION_ARGS)
 		ereport(ERROR,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 			 errmsg("WAL level not sufficient for creating a restore point"),
-				 errhint("wal_level must be set to \"archive\", \"hot_standby\", or \"logical\" at server start.")));
+				 errhint("wal_level must be set to \"replica\" or \"logical\" at server start.")));
 
 	restore_name_str = text_to_cstring(restore_name);
 

src/backend/postmaster/postmaster.c

@@ -858,7 +858,7 @@ PostmasterMain(int argc, char *argv[])
 				(errmsg("WAL archival cannot be enabled when wal_level is \"minimal\"")));
 	if (max_wal_senders > 0 && wal_level == WAL_LEVEL_MINIMAL)
 		ereport(ERROR,
-				(errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"archive\", \"hot_standby\", or \"logical\"")));
+				(errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"replica\" or \"logical\"")));
 
 	/*
 	 * Other one-time internal sanity checks can go here, if they are fast.

src/backend/replication/slot.c

@@ -760,7 +760,7 @@ CheckSlotRequirements(void)
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 (errmsg("replication slots can only be used if max_replication_slots > 0"))));
 
-	if (wal_level < WAL_LEVEL_ARCHIVE)
+	if (wal_level < WAL_LEVEL_REPLICA)
 		ereport(ERROR,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("replication slots can only be used if wal_level >= archive")));

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

@@ -173,7 +173,7 @@
 
 # - Settings -
 
-#wal_level = minimal			# minimal, archive, hot_standby, or logical
+#wal_level = minimal			# minimal, replica, or logical
 					# (change requires restart)
 #fsync = on				# turns forced synchronization on or off
 #synchronous_commit = on		# synchronization level;

src/bin/pg_basebackup/t/010_pg_basebackup.pl

@@ -43,7 +43,7 @@ $node->command_fails(
 open CONF, ">>$pgdata/postgresql.conf";
 print CONF "max_replication_slots = 10\n";
 print CONF "max_wal_senders = 10\n";
-print CONF "wal_level = archive\n";
+print CONF "wal_level = replica\n";
 close CONF;
 $node->restart;
 

src/bin/pg_controldata/pg_controldata.c

@@ -73,10 +73,8 @@ wal_level_str(WalLevel wal_level)
 	{
 		case WAL_LEVEL_MINIMAL:
 			return "minimal";
-		case WAL_LEVEL_ARCHIVE:
-			return "archive";
-		case WAL_LEVEL_HOT_STANDBY:
-			return "hot_standby";
+		case WAL_LEVEL_REPLICA:
+			return "replica";
 		case WAL_LEVEL_LOGICAL:
 			return "logical";
 	}

src/include/access/xlog.h

@@ -121,25 +121,24 @@ extern int	XLogArchiveMode;
 typedef enum WalLevel
 {
 	WAL_LEVEL_MINIMAL = 0,
-	WAL_LEVEL_ARCHIVE,
-	WAL_LEVEL_HOT_STANDBY,
+	WAL_LEVEL_REPLICA,
 	WAL_LEVEL_LOGICAL
 } WalLevel;
 extern int	wal_level;
 
 /* Is WAL archiving enabled (always or only while server is running normally)? */
 #define XLogArchivingActive() \
-	(XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level >= WAL_LEVEL_ARCHIVE)
+	(AssertMacro(XLogArchiveMode == ARCHIVE_MODE_OFF || wal_level >= WAL_LEVEL_REPLICA), XLogArchiveMode > ARCHIVE_MODE_OFF)
 /* Is WAL archiving enabled always (even during recovery)? */
 #define XLogArchivingAlways() \
-	(XLogArchiveMode == ARCHIVE_MODE_ALWAYS && wal_level >= WAL_LEVEL_ARCHIVE)
+	(AssertMacro(XLogArchiveMode == ARCHIVE_MODE_OFF || wal_level >= WAL_LEVEL_REPLICA), XLogArchiveMode == ARCHIVE_MODE_ALWAYS)
 #define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0')
 
 /*
  * Is WAL-logging necessary for archival or log-shipping, or can we skip
  * WAL-logging if we fsync() the data before committing instead?
  */
-#define XLogIsNeeded() (wal_level >= WAL_LEVEL_ARCHIVE)
+#define XLogIsNeeded() (wal_level >= WAL_LEVEL_REPLICA)
 
 /*
  * Is a full-page image needed for hint bit updates?
@@ -153,7 +152,7 @@ extern int	wal_level;
 #define XLogHintBitIsNeeded() (DataChecksumsEnabled() || wal_log_hints)
 
 /* Do we need to WAL-log information required only for Hot Standby and logical replication? */
-#define XLogStandbyInfoActive() (wal_level >= WAL_LEVEL_HOT_STANDBY)
+#define XLogStandbyInfoActive() (wal_level >= WAL_LEVEL_REPLICA)
 
 /* Do we need to WAL-log information required only for logical replication? */
 #define XLogLogicalInfoActive() (wal_level >= WAL_LEVEL_LOGICAL)

src/include/catalog/pg_control.h

@@ -54,7 +54,7 @@ typedef struct CheckPoint
 	/*
 	 * Oldest XID still running. This is only needed to initialize hot standby
 	 * mode from an online checkpoint, so we only bother calculating this for
-	 * online checkpoints and only when wal_level is hot_standby. Otherwise
+	 * online checkpoints and only when wal_level is replica. Otherwise
 	 * it's set to InvalidTransactionId.
 	 */
 	TransactionId oldestActiveXid;

src/test/perl/PostgresNode.pm

@@ -404,7 +404,7 @@ sub init
 
 	if ($params{allows_streaming})
 	{
-		print $conf "wal_level = hot_standby\n";
+		print $conf "wal_level = replica\n";
 		print $conf "max_wal_senders = 5\n";
 		print $conf "wal_keep_segments = 20\n";
 		print $conf "max_wal_size = 128MB\n";