Fix replica identity check for MERGE command

This commit enforces proper checks for MERGE command to determine if it can be
executed with current replica identity. It ensures that each conditional MERGE
action (insert, update, delete) undergoes the same check as individual
DML commands.

Author: Zhijie Hou

src/backend/executor/execMain.c

@@ -1059,7 +1059,11 @@ CheckValidResultRel(ResultRelInfo *resultRelInfo, CmdType operation,
 	{
 		case RELKIND_RELATION:
 		case RELKIND_PARTITIONED_TABLE:
-			CheckCmdReplicaIdentity(resultRel, operation);
+			if (operation == CMD_MERGE)
+				foreach_node(MergeAction, action, mergeActions)
+					CheckCmdReplicaIdentity(resultRel, action->commandType);
+			else
+				CheckCmdReplicaIdentity(resultRel, operation);
 			break;
 		case RELKIND_SEQUENCE:
 			ereport(ERROR,

src/test/regress/expected/publication.out

@@ -1924,6 +1924,32 @@ DROP PUBLICATION pub1;
 DROP PUBLICATION pub2;
 DROP TABLE gencols;
 RESET client_min_messages;
+-- Test that the MERGE command correctly checks REPLICA IDENTITY when the
+-- target table is published.
+CREATE TABLE testpub_merge_no_ri (a int, b int);
+CREATE TABLE testpub_merge_pk (a int primary key, b int);
+SET client_min_messages = 'ERROR';
+CREATE PUBLICATION pub1 FOR ALL TABLES;
+RESET client_min_messages;
+-- fail - missing REPLICA IDENTITY
+MERGE INTO testpub_merge_no_ri USING testpub_merge_pk s ON s.a >= 1
+ WHEN MATCHED THEN UPDATE SET b = s.b;
+ERROR:  cannot update table "testpub_merge_no_ri" because it does not have a replica identity and publishes updates
+HINT:  To enable updating the table, set REPLICA IDENTITY using ALTER TABLE.
+-- fail - missing REPLICA IDENTITY
+MERGE INTO testpub_merge_no_ri USING testpub_merge_pk s ON s.a >= 1
+ WHEN MATCHED THEN DELETE;
+ERROR:  cannot delete from table "testpub_merge_no_ri" because it does not have a replica identity and publishes deletes
+HINT:  To enable deleting from the table, set REPLICA IDENTITY using ALTER TABLE.
+-- ok - inserts are not restricted
+MERGE INTO testpub_merge_no_ri USING testpub_merge_pk s ON s.a >= 1
+ WHEN NOT MATCHED THEN INSERT (a, b) VALUES (0, 0);
+-- ok - REPLICA IDENTITY is DEFAULT and table has a PK
+MERGE INTO testpub_merge_pk USING testpub_merge_no_ri s ON s.a >= 1
+ WHEN MATCHED THEN UPDATE SET b = s.b;
+DROP PUBLICATION pub1;
+DROP TABLE testpub_merge_no_ri;
+DROP TABLE testpub_merge_pk;
 RESET SESSION AUTHORIZATION;
 DROP ROLE regress_publication_user, regress_publication_user2;
 DROP ROLE regress_publication_user_dummy;

src/test/regress/sql/publication.sql

@@ -1223,6 +1223,36 @@ DROP PUBLICATION pub2;
 DROP TABLE gencols;
 
 RESET client_min_messages;
+
+-- Test that the MERGE command correctly checks REPLICA IDENTITY when the
+-- target table is published.
+CREATE TABLE testpub_merge_no_ri (a int, b int);
+CREATE TABLE testpub_merge_pk (a int primary key, b int);
+
+SET client_min_messages = 'ERROR';
+CREATE PUBLICATION pub1 FOR ALL TABLES;
+RESET client_min_messages;
+
+-- fail - missing REPLICA IDENTITY
+MERGE INTO testpub_merge_no_ri USING testpub_merge_pk s ON s.a >= 1
+ WHEN MATCHED THEN UPDATE SET b = s.b;
+
+-- fail - missing REPLICA IDENTITY
+MERGE INTO testpub_merge_no_ri USING testpub_merge_pk s ON s.a >= 1
+ WHEN MATCHED THEN DELETE;
+
+-- ok - inserts are not restricted
+MERGE INTO testpub_merge_no_ri USING testpub_merge_pk s ON s.a >= 1
+ WHEN NOT MATCHED THEN INSERT (a, b) VALUES (0, 0);
+
+-- ok - REPLICA IDENTITY is DEFAULT and table has a PK
+MERGE INTO testpub_merge_pk USING testpub_merge_no_ri s ON s.a >= 1
+ WHEN MATCHED THEN UPDATE SET b = s.b;
+
+DROP PUBLICATION pub1;
+DROP TABLE testpub_merge_no_ri;
+DROP TABLE testpub_merge_pk;
+
 RESET SESSION AUTHORIZATION;
 DROP ROLE regress_publication_user, regress_publication_user2;
 DROP ROLE regress_publication_user_dummy;