Ignore dropped columns during apply of update/delete.

We fail to apply updates and deletes when the REPLICA IDENTITY FULL is
used for the table having dropped columns. We didn't use to ignore dropped
columns while doing tuple comparison among the tuples from the publisher
and subscriber during apply of updates and deletes.

Author: Onder Kalaci, Shi yu
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CACawEhVQC9WoofunvXg12aXtbqKnEgWxoRx3+v8q32AWYsdpGg@mail.gmail.com

src/backend/executor/execReplication.c

@@ -289,6 +289,14 @@ tuples_equal(TupleTableSlot *slot1, TupleTableSlot *slot2,
 		Form_pg_attribute att;
 		TypeCacheEntry *typentry;
 
+		att = TupleDescAttr(slot1->tts_tupleDescriptor, attrnum);
+
+		/*
+		 * Ignore dropped columns as the publisher doesn't send those
+		 */
+		if (att->attisdropped)
+			continue;
+
 		/*
 		 * If one value is NULL and other is not, then they are certainly not
 		 * equal
@@ -302,8 +310,6 @@ tuples_equal(TupleTableSlot *slot1, TupleTableSlot *slot2,
 		if (slot1->tts_isnull[attrnum] || slot2->tts_isnull[attrnum])
 			continue;
 
-		att = TupleDescAttr(slot1->tts_tupleDescriptor, attrnum);
-
 		typentry = eq[attrnum];
 		if (typentry == NULL)
 		{

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

@@ -370,6 +370,61 @@ $result = $node_subscriber->safe_psql('postgres', "SELECT * FROM sch2.t1");
 is( $result, qq(1
 3), 'check data in subscriber sch2.t1 after schema rename');
 
+# Again, drop replication state but not tables.
+$node_subscriber->safe_psql('postgres', "DROP SUBSCRIPTION tap_sub_sch");
+$node_publisher->safe_psql('postgres', "DROP PUBLICATION tap_pub_sch");
+
+$node_publisher->stop('fast');
+$node_subscriber->stop('fast');
+
+# The bug was that when the REPLICA IDENTITY FULL is used with dropped columns,
+# we fail to apply updates and deletes
+$node_publisher->rotate_logfile();
+$node_publisher->start();
+
+$node_subscriber->rotate_logfile();
+$node_subscriber->start();
+
+$node_publisher->safe_psql(
+	'postgres', qq(
+	CREATE TABLE dropped_cols (a int, b_drop int, c int);
+	ALTER TABLE dropped_cols REPLICA IDENTITY FULL;
+	CREATE PUBLICATION pub_dropped_cols FOR TABLE dropped_cols;
+	-- some initial data
+	INSERT INTO dropped_cols VALUES (1, 1, 1);
+));
+
+$node_subscriber->safe_psql(
+	'postgres', qq(
+	 CREATE TABLE dropped_cols (a int, b_drop int, c int);
+));
+
+$publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
+$node_subscriber->safe_psql('postgres',
+	"CREATE SUBSCRIPTION sub_dropped_cols CONNECTION '$publisher_connstr' PUBLICATION pub_dropped_cols"
+);
+$node_subscriber->wait_for_subscription_sync;
+
+$node_publisher->safe_psql(
+	'postgres', qq(
+		ALTER TABLE dropped_cols DROP COLUMN b_drop;
+));
+$node_subscriber->safe_psql(
+	'postgres', qq(
+		ALTER TABLE dropped_cols DROP COLUMN b_drop;
+));
+
+$node_publisher->safe_psql(
+	'postgres', qq(
+		UPDATE dropped_cols SET a = 100;
+));
+$node_publisher->wait_for_catchup('sub_dropped_cols');
+
+is( $node_subscriber->safe_psql(
+		'postgres', "SELECT count(*) FROM dropped_cols WHERE a = 100"),
+	qq(1),
+	'replication with RI FULL and dropped columns');
+
 $node_publisher->stop('fast');
 $node_subscriber->stop('fast');