From b7658c24c7c1ffad131a7fdf67ce7fc008be1177 Mon Sep 17 00:00:00 2001
From: Amit Kapila <akapila@postgresql.org>
Date: Thu, 16 Jun 2022 08:45:07 +0530
Subject: [PATCH] Fix data inconsistency between publisher and subscriber.

We were not updating the partition map cache in the subscriber even when
the corresponding remote rel is changed. Due to this data was getting
incorrectly replicated for partition tables after the publisher has
changed the table schema.

Fix it by resetting the required entries in the partition map cache after
receiving a new relation mapping from the publisher.

Reported-by: Shi Yu
Author: Shi Yu, Hou Zhijie
Reviewed-by: Amit Langote, Amit Kapila
Backpatch-through: 13, where it was introduced
Discussion: https://postgr.es/m/OSZPR01MB6310F46CD425A967E4AEF736FDA49@OSZPR01MB6310.jpnprd01.prod.outlook.com
---
 src/backend/replication/logical/relation.c | 34 ++++++++++++++++++++++
 src/backend/replication/logical/worker.c   |  3 ++
 src/include/replication/logicalrelation.h  |  1 +
 src/test/subscription/t/013_partition.pl   | 15 ++++++++++
 4 files changed, 53 insertions(+)

diff --git a/src/backend/replication/logical/relation.c b/src/backend/replication/logical/relation.c
index 9c9ec144d8b..34c55c04e30 100644
--- a/src/backend/replication/logical/relation.c
+++ b/src/backend/replication/logical/relation.c
@@ -486,6 +486,40 @@ logicalrep_partmap_invalidate_cb(Datum arg, Oid reloid)
 	}
 }
 
+/*
+ * Reset the entries in the partition map that refer to remoterel.
+ *
+ * Called when new relation mapping is sent by the publisher to update our
+ * expected view of incoming data from said publisher.
+ *
+ * Note that we don't update the remoterel information in the entry here,
+ * we will update the information in logicalrep_partition_open to avoid
+ * unnecessary work.
+ */
+void
+logicalrep_partmap_reset_relmap(LogicalRepRelation *remoterel)
+{
+	HASH_SEQ_STATUS status;
+	LogicalRepPartMapEntry *part_entry;
+	LogicalRepRelMapEntry *entry;
+
+	if (LogicalRepPartMap == NULL)
+		return;
+
+	hash_seq_init(&status, LogicalRepPartMap);
+	while ((part_entry = (LogicalRepPartMapEntry *) hash_seq_search(&status)) != NULL)
+	{
+		entry = &part_entry->relmapentry;
+
+		if (entry->remoterel.remoteid != remoterel->remoteid)
+			continue;
+
+		logicalrep_relmap_free_entry(entry);
+
+		memset(entry, 0, sizeof(LogicalRepRelMapEntry));
+	}
+}
+
 /*
  * Initialize the partition map cache.
  */
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index fc210a9e7b9..607f719fd61 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -1562,6 +1562,9 @@ apply_handle_relation(StringInfo s)
 
 	rel = logicalrep_read_rel(s);
 	logicalrep_relmap_update(rel);
+
+	/* Also reset all entries in the partition map that refer to remoterel. */
+	logicalrep_partmap_reset_relmap(rel);
 }
 
 /*
diff --git a/src/include/replication/logicalrelation.h b/src/include/replication/logicalrelation.h
index 7bf8cd22bd4..78cd7e77f54 100644
--- a/src/include/replication/logicalrelation.h
+++ b/src/include/replication/logicalrelation.h
@@ -38,6 +38,7 @@ typedef struct LogicalRepRelMapEntry
 } LogicalRepRelMapEntry;
 
 extern void logicalrep_relmap_update(LogicalRepRelation *remoterel);
+extern void logicalrep_partmap_reset_relmap(LogicalRepRelation *remoterel);
 
 extern LogicalRepRelMapEntry *logicalrep_rel_open(LogicalRepRelId remoteid,
 												  LOCKMODE lockmode);
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 06f92150184..69f4009a14a 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -853,4 +853,19 @@ $result = $node_subscriber2->safe_psql('postgres',
 	"SELECT a, b, c FROM tab5 ORDER BY 1");
 is($result, qq(3|1|), 'updates of tab5 replicated correctly after altering table on subscriber');
 
+# Test that replication into the partitioned target table continues to
+# work correctly when the published table is altered.
+$node_publisher->safe_psql(
+	'postgres', q{
+	ALTER TABLE tab5 DROP COLUMN b, ADD COLUMN c INT;
+	ALTER TABLE tab5 ADD COLUMN b INT;});
+
+$node_publisher->safe_psql('postgres', "UPDATE tab5 SET c = 1 WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub2');
+
+$result = $node_subscriber2->safe_psql('postgres',
+	"SELECT a, b, c FROM tab5 ORDER BY 1");
+is($result, qq(3||1), 'updates of tab5 replicated correctly after altering table on publisher');
+
 done_testing();