Do not acquire locks if the index does not exist

src/backend/distributed/commands/index.c

@@ -748,16 +748,6 @@ PreprocessDropIndexStmt(Node *node, const char *dropIndexCommand,
 			lockmode = ShareUpdateExclusiveLock;
 		}
 
-		/*
-		 * Acquire global lock to prevent concurrent writes or DDL. However,
-		 * we do not bother for DROP INDEX CONCURRENTLY, since we'll have
-		 * to release the lock.
-		 */
-		if (!dropIndexStatement->concurrent)
-		{
-			AcquireDistributedLockOnRelations(list_make1(rangeVar), lockmode, 0);
-		}
-
 		/*
 		 * The next few statements are based on RemoveRelations() in
 		 * commands/tablecmds.c in Postgres source.
@@ -781,6 +771,16 @@ PreprocessDropIndexStmt(Node *node, const char *dropIndexCommand,
 			continue;
 		}
 
+		/*
+		 * Acquire global lock to prevent concurrent writes or DDL. However,
+		 * we do not bother for DROP INDEX CONCURRENTLY, since we'll have
+		 * to release the lock.
+		 */
+		if (!dropIndexStatement->concurrent)
+		{
+			AcquireDistributedLockOnRelations(list_make1(rangeVar), lockmode, 0);
+		}
+
 		Oid relationId = IndexGetRelation(indexId, false);
 		bool isCitusRelation = IsCitusTable(relationId);
 		if (isCitusRelation)

src/test/regress/expected/isolation_drop_vs_all.out

@@ -68,8 +68,9 @@ step s2-begin: BEGIN;
 step s1-drop: DROP TABLE drop_hash;
 step s2-ddl-create-index: CREATE INDEX drop_hash_index ON drop_hash(id); <waiting ...>
 step s1-commit: COMMIT;
+s2: WARNING:  relation "drop_tests.drop_hash" does not exist
 step s2-ddl-create-index: <... completed>
-ERROR:  relation "drop_hash" does not exist
+ERROR:  failure on connection marked as essential: localhost:xxxxx
 step s2-commit: COMMIT;
 step s1-select-count: SELECT COUNT(*) FROM drop_hash;
 ERROR:  relation "drop_hash" does not exist

src/test/regress/expected/isolation_multiuser_locking.out

@@ -140,7 +140,7 @@ step s2-begin:
 step s2-index:
 	CREATE INDEX test_index ON test_table(column1);
 
-ERROR:  must be owner of table test_table
+ERROR:  permission denied for table test_table
 step s1-insert:
 	UPDATE test_table SET column2 = 1;