From 4d8d7ef3a565c53b7b463b609995276fc16f1f82 Mon Sep 17 00:00:00 2001
From: Onder Kalaci <onderkalaci@gmail.com>
Date: Thu, 16 Mar 2023 18:06:54 +0300
Subject: [PATCH v4] Ignore dropped columns when REPLICA IDENTITY FULL

Dropped columns are filled with NULL values on slot_store_data()
but not on table_scan_getnextslot(). With this commit, we skip
such columns while checking tuple equality.
---
 src/backend/executor/execReplication.c | 10 ++++-
 src/test/subscription/t/100_bugs.pl    | 55 ++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index fa8628e3e1..652732c6ed 100644
--- a/src/backend/executor/execReplication.c
+++ b/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)
 		{
diff --git a/src/test/subscription/t/100_bugs.pl b/src/test/subscription/t/100_bugs.pl
index 036576acab..549a1b5fe3 100644
--- a/src/test/subscription/t/100_bugs.pl
+++ b/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');
 
-- 
2.31.1