Fix relation descriptor leak.

We missed closing the relation descriptor while sending changes via the
root of partitioned relations during logical replication.

Author: Amit Langote and Mark Zhao
Reviewed-by: Amit Kapila and Ashutosh Bapat
Backpatch-through: 13, where it was introduced
Discussion: https://postgr.es/m/tencent_41FEA657C206F19AB4F406BE9252A0F69C06@qq.com
Discussion: https://postgr.es/m/tencent_6E296D2F7D70AFC90D83353B69187C3AA507@qq.com

Author: Amit Kapila

src/backend/replication/pgoutput/pgoutput.c

@@ -363,6 +363,7 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 	PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
 	MemoryContext old;
 	RelationSyncEntry *relentry;
+	Relation	ancestor = NULL;
 
 	if (!is_publishable_relation(relation))
 		return;
@@ -404,7 +405,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 				if (relentry->publish_as_relid != RelationGetRelid(relation))
 				{
 					Assert(relation->rd_rel->relispartition);
-					relation = RelationIdGetRelation(relentry->publish_as_relid);
+					ancestor = RelationIdGetRelation(relentry->publish_as_relid);
+					relation = ancestor;
 					/* Convert tuple if needed. */
 					if (relentry->map)
 						tuple = execute_attr_map_tuple(tuple, relentry->map);
@@ -425,7 +427,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 				if (relentry->publish_as_relid != RelationGetRelid(relation))
 				{
 					Assert(relation->rd_rel->relispartition);
-					relation = RelationIdGetRelation(relentry->publish_as_relid);
+					ancestor = RelationIdGetRelation(relentry->publish_as_relid);
+					relation = ancestor;
 					/* Convert tuples if needed. */
 					if (relentry->map)
 					{
@@ -448,7 +451,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 				if (relentry->publish_as_relid != RelationGetRelid(relation))
 				{
 					Assert(relation->rd_rel->relispartition);
-					relation = RelationIdGetRelation(relentry->publish_as_relid);
+					ancestor = RelationIdGetRelation(relentry->publish_as_relid);
+					relation = ancestor;
 					/* Convert tuple if needed. */
 					if (relentry->map)
 						oldtuple = execute_attr_map_tuple(oldtuple, relentry->map);
@@ -465,6 +469,12 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 			Assert(false);
 	}
 
+	if (RelationIsValid(ancestor))
+	{
+		RelationClose(ancestor);
+		ancestor = NULL;
+	}
+
 	/* Cleanup */
 	MemoryContextSwitchTo(old);
 	MemoryContextReset(data->context);