Fix the handling of the failover option in subscription commands.

Do not allow ALTER SUBSCRIPTION ... SET (failover = on|off) in a
transaction block as the changed failover option of the slot can't be
rolled back. For the same reason, we refrain from altering the replication
slot's failover property if the subscription is created with a valid
slot_name and create_slot=false.

Reprted-by: Kuroda Hayato
Author: Hou Zhijie
Reviewed-by: Shveta Malik, Bertrand Drouvot, Kuroda Hayato
Discussion: https://postgr.es/m/OS0PR01MB57165542B09DFA4943830BF294082@OS0PR01MB5716.jpnprd01.prod.outlook.com

5 files changed, 31 insertions, 57 deletions

diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index 5a47fa984df..e407428dbcf 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -401,13 +401,6 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 					 errmsg("%s and %s are mutually exclusive options",
 							"connect = false", "copy_data = true")));
 
-		if (opts->failover &&
-			IsSet(opts->specified_opts, SUBOPT_FAILOVER))
-			ereport(ERROR,
-					(errcode(ERRCODE_SYNTAX_ERROR),
-					 errmsg("%s and %s are mutually exclusive options",
-							"connect = false", "failover = true")));
-
 		/* Change the defaults of other options. */
 		opts->enabled = false;
 		opts->create_slot = false;
@@ -836,21 +829,6 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 						(errmsg("created replication slot \"%s\" on publisher",
 								opts.slot_name)));
 			}
-
-			/*
-			 * If the slot_name is specified without the create_slot option,
-			 * it is possible that the user intends to use an existing slot on
-			 * the publisher, so here we alter the failover property of the
-			 * slot to match the failover value in subscription.
-			 *
-			 * We do not need to change the failover to false if the server
-			 * does not support failover (e.g. pre-PG17).
-			 */
-			else if (opts.slot_name &&
-					 (opts.failover || walrcv_server_version(wrconn) >= 170000))
-			{
-				walrcv_alter_slot(wrconn, opts.slot_name, opts.failover);
-			}
 		}
 		PG_FINALLY();
 		{
@@ -1267,6 +1245,12 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								 errmsg("cannot set %s for enabled subscription",
 										"failover")));
 
+					/*
+					 * The changed failover option of the slot can't be rolled
+					 * back.
+					 */
+					PreventInTransactionBlock(isTopLevel, "ALTER SUBSCRIPTION ... SET (failover)");
+
 					values[Anum_pg_subscription_subfailover - 1] =
 						BoolGetDatum(opts.failover);
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index ed9bab3bfe5..b8acdd73551 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4804,12 +4804,17 @@ getSubscriptions(Archive *fout)
 
 	if (dopt->binary_upgrade && fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query, " o.remote_lsn AS suboriginremotelsn,\n"
-							 " s.subenabled,\n"
-							 " s.subfailover\n");
+							 " s.subenabled,\n");
 	else
 		appendPQExpBufferStr(query, " NULL AS suboriginremotelsn,\n"
-							 " false AS subenabled,\n"
-							 " false AS subfailover\n");
+							 " false AS subenabled,\n");
+
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subfailover\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subfailover\n");
 
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
@@ -5132,6 +5137,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subrunasowner, "t") == 0)
 		appendPQExpBufferStr(query, ", run_as_owner = true");
 
+	if (strcmp(subinfo->subfailover, "t") == 0)
+		appendPQExpBufferStr(query, ", failover = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
@@ -5165,17 +5173,6 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 			appendPQExpBuffer(query, ", '%s');\n", subinfo->suboriginremotelsn);
 		}
 
-		if (strcmp(subinfo->subfailover, "t") == 0)
-		{
-			/*
-			 * Enable the failover to allow the subscription's slot to be
-			 * synced to the standbys after the upgrade.
-			 */
-			appendPQExpBufferStr(query,
-								 "\n-- For binary upgrade, must preserve the subscriber's failover option.\n");
-			appendPQExpBuffer(query, "ALTER SUBSCRIPTION %s SET(failover = true);\n", qsubname);
-		}
-
 		if (strcmp(subinfo->subenabled, "t") == 0)
 		{
 			/*
diff --git a/src/test/recovery/t/040_standby_failover_slots_sync.pl b/src/test/recovery/t/040_standby_failover_slots_sync.pl
index 76545e3c74a..12acf874d70 100644
--- a/src/test/recovery/t/040_standby_failover_slots_sync.pl
+++ b/src/test/recovery/t/040_standby_failover_slots_sync.pl
@@ -42,26 +42,12 @@ my $slot_creation_time_on_primary = $publisher->safe_psql(
     SELECT current_timestamp;
 ]);
 
-# Create a slot on the publisher with failover disabled
-$publisher->safe_psql('postgres',
-	"SELECT 'init' FROM pg_create_logical_replication_slot('lsub1_slot', 'pgoutput', false, false, false);"
-);
-
-# Confirm that the failover flag on the slot is turned off
-is( $publisher->safe_psql(
-		'postgres',
-		q{SELECT failover from pg_replication_slots WHERE slot_name = 'lsub1_slot';}
-	),
-	"f",
-	'logical slot has failover false on the publisher');
-
-# Create a subscription (using the same slot created above) that enables
-# failover.
+# Create a subscription that enables failover.
 $subscriber1->safe_psql('postgres',
-	"CREATE SUBSCRIPTION regress_mysub1 CONNECTION '$publisher_connstr' PUBLICATION regress_mypub WITH (slot_name = lsub1_slot, copy_data=false, failover = true, create_slot = false, enabled = false);"
+	"CREATE SUBSCRIPTION regress_mysub1 CONNECTION '$publisher_connstr' PUBLICATION regress_mypub WITH (slot_name = lsub1_slot, copy_data = false, failover = true, enabled = false);"
 );
 
-# Confirm that the failover flag on the slot has now been turned on
+# Confirm that the failover flag on the slot is turned on
 is( $publisher->safe_psql(
 		'postgres',
 		q{SELECT failover from pg_replication_slots WHERE slot_name = 'lsub1_slot';}
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 1eee6b17b8f..0f2a25cdc19 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -89,8 +89,6 @@ CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PU
 ERROR:  connect = false and enabled = true are mutually exclusive options
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, create_slot = true);
 ERROR:  connect = false and create_slot = true are mutually exclusive options
-CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, failover = true);
-ERROR:  connect = false and failover = true are mutually exclusive options
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (slot_name = NONE, enabled = true);
 ERROR:  slot_name = NONE and enabled = true are mutually exclusive options
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (slot_name = NONE, enabled = false, create_slot = true);
@@ -472,6 +470,11 @@ REVOKE CREATE ON DATABASE REGRESSION FROM regress_subscription_user3;
 SET SESSION AUTHORIZATION regress_subscription_user3;
 ALTER SUBSCRIPTION regress_testsub RENAME TO regress_testsub2;
 ERROR:  permission denied for database regression
+-- fail - cannot do ALTER SUBSCRIPTION SET (failover) inside transaction block
+BEGIN;
+ALTER SUBSCRIPTION regress_testsub SET (failover);
+ERROR:  ALTER SUBSCRIPTION ... SET (failover) cannot run inside a transaction block
+COMMIT;
 -- ok, owning it is enough for this stuff
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 1b2a23ba7bf..3e5ba4cb8c6 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -54,7 +54,6 @@ SET SESSION AUTHORIZATION 'regress_subscription_user';
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, copy_data = true);
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, enabled = true);
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, create_slot = true);
-CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, failover = true);
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (slot_name = NONE, enabled = true);
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (slot_name = NONE, enabled = false, create_slot = true);
 CREATE SUBSCRIPTION regress_testsub2 CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (slot_name = NONE);
@@ -333,6 +332,11 @@ REVOKE CREATE ON DATABASE REGRESSION FROM regress_subscription_user3;
 SET SESSION AUTHORIZATION regress_subscription_user3;
 ALTER SUBSCRIPTION regress_testsub RENAME TO regress_testsub2;
 
+-- fail - cannot do ALTER SUBSCRIPTION SET (failover) inside transaction block
+BEGIN;
+ALTER SUBSCRIPTION regress_testsub SET (failover);
+COMMIT;
+
 -- ok, owning it is enough for this stuff
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;