Invalidate relcache when changing REPLICA IDENTITY index.

When changing REPLICA IDENTITY INDEX to another one, the target table's
relcache was not being invalidated. This leads to skipping update/delete
operations during apply on the subscriber side as the columns required to
search corresponding rows won't get logged.

Author: Tang Haiying, Hou Zhijie
Reviewed-by: Euler Taveira, Amit Kapila
Backpatch-through: 10
Discussion: https://postgr.es/m/OS0PR01MB61133CA11630DAE45BC6AD95FB939@OS0PR01MB6113.jpnprd01.prod.outlook.com

src/backend/commands/tablecmds.c

@@ -15488,6 +15488,12 @@ relation_mark_replica_identity(Relation rel, char ri_type, Oid indexOid,
 			CatalogTupleUpdate(pg_index, &pg_index_tuple->t_self, pg_index_tuple);
 			InvokeObjectPostAlterHookArg(IndexRelationId, thisIndexOid, 0,
 										 InvalidOid, is_internal);
+			/*
+			 * Invalidate the relcache for the table, so that after we commit
+			 * all sessions will refresh the table's replica identity index
+			 * before attempting any UPDATE or DELETE on the table.
+			 */
+			CacheInvalidateRelcache(rel);
 		}
 		heap_freetuple(pg_index_tuple);
 	}

src/test/subscription/t/100_bugs.pl

@@ -6,7 +6,7 @@ use strict;
 use warnings;
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
-use Test::More tests => 5;
+use Test::More tests => 7;
 
 # Bug #15114
 
@@ -224,3 +224,85 @@ $node_sub->safe_psql('postgres', "DROP TABLE tab1");
 $node_pub->stop('fast');
 $node_pub_sub->stop('fast');
 $node_sub->stop('fast');
+
+# https://postgr.es/m/OS0PR01MB61133CA11630DAE45BC6AD95FB939%40OS0PR01MB6113.jpnprd01.prod.outlook.com
+
+# The bug was that when changing the REPLICA IDENTITY INDEX to another one, the
+# target table's relcache was not being invalidated. This leads to skipping
+# UPDATE/DELETE operations during apply on the subscriber side as the columns
+# required to search corresponding rows won't get logged.
+$node_publisher = PostgreSQL::Test::Cluster->new('publisher3');
+$node_publisher->init(allows_streaming => 'logical');
+$node_publisher->start;
+
+$node_subscriber = PostgreSQL::Test::Cluster->new('subscriber3');
+$node_subscriber->init(allows_streaming => 'logical');
+$node_subscriber->start;
+
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE tab_replidentity_index(a int not null, b int not null)");
+$node_publisher->safe_psql('postgres',
+	"CREATE UNIQUE INDEX idx_replidentity_index_a ON tab_replidentity_index(a)"
+);
+$node_publisher->safe_psql('postgres',
+	"CREATE UNIQUE INDEX idx_replidentity_index_b ON tab_replidentity_index(b)"
+);
+
+# use index idx_replidentity_index_a as REPLICA IDENTITY on publisher.
+$node_publisher->safe_psql('postgres',
+	"ALTER TABLE tab_replidentity_index REPLICA IDENTITY USING INDEX idx_replidentity_index_a"
+);
+
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO tab_replidentity_index VALUES(1, 1),(2, 2)");
+
+$node_subscriber->safe_psql('postgres',
+	"CREATE TABLE tab_replidentity_index(a int not null, b int not null)");
+$node_subscriber->safe_psql('postgres',
+	"CREATE UNIQUE INDEX idx_replidentity_index_a ON tab_replidentity_index(a)"
+);
+$node_subscriber->safe_psql('postgres',
+	"CREATE UNIQUE INDEX idx_replidentity_index_b ON tab_replidentity_index(b)"
+);
+# use index idx_replidentity_index_b as REPLICA IDENTITY on subscriber because
+# it reflects the future scenario we are testing: changing REPLICA IDENTITY
+# INDEX.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE tab_replidentity_index REPLICA IDENTITY USING INDEX idx_replidentity_index_b"
+);
+
+$publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
+$node_publisher->safe_psql('postgres',
+	"CREATE PUBLICATION tap_pub FOR TABLE tab_replidentity_index");
+$node_subscriber->safe_psql('postgres',
+	"CREATE SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr' PUBLICATION tap_pub"
+);
+
+$node_publisher->wait_for_catchup('tap_sub');
+
+# Also wait for initial table sync to finish
+$node_subscriber->poll_query_until('postgres', $synced_query)
+  or die "Timed out while waiting for subscriber to synchronize data";
+
+is( $node_subscriber->safe_psql(
+		'postgres', "SELECT * FROM tab_replidentity_index"),
+	qq(1|1
+2|2),
+	"check initial data on subscriber");
+
+# Set REPLICA IDENTITY to idx_replidentity_index_b on publisher, then run UPDATE and DELETE.
+$node_publisher->safe_psql(
+	'postgres', qq[
+	ALTER TABLE tab_replidentity_index REPLICA IDENTITY USING INDEX idx_replidentity_index_b;
+	UPDATE tab_replidentity_index SET a = -a WHERE a = 1;
+	DELETE FROM tab_replidentity_index WHERE a = 2;
+]);
+
+$node_publisher->wait_for_catchup('tap_sub');
+is( $node_subscriber->safe_psql(
+		'postgres', "SELECT * FROM tab_replidentity_index"),
+	qq(-1|1),
+	"update works with REPLICA IDENTITY");
+
+$node_publisher->stop('fast');
+$node_subscriber->stop('fast');