Fix empty FROM clauses in PG12

src/backend/distributed/planner/function_call_delegation.c

@@ -156,24 +156,45 @@ TryToDelegateFunctionCall(Query *query, bool *hasExternParam)
 
 	if (joinTree->fromlist != NIL)
 	{
-		/* query has a FROM section */
 #if PG_VERSION_NUM >= 120000
 
-		/* in pg12 empty FROMs are represented with an RTE_RESULT */
+		/*
+		 * In pg12's planning phase empty FROMs are represented with an RTE_RESULT.
+		 * When we arrive here, standard_planner has already been called which calls
+		 * replace_empty_jointree() which replaces empty fromlist with a list of
+		 * single RTE_RESULT RangleTableRef node.
+		 */
 		if (list_length(joinTree->fromlist) == 1)
 		{
 			RangeTblRef *reference = linitial(joinTree->fromlist);
+
+			if (IsA(reference, RangeTblRef))
+			{
 				RangeTblEntry *rtentry = rt_fetch(reference->rtindex, query->rtable);
 				if (rtentry->rtekind != RTE_RESULT)
 				{
+					/* e.g. SELECT f() FROM rel */
 					return NULL;
 				}
 			}
 			else
 			{
+				/*
+				 * e.g. IsA(reference, JoinExpr). This is explicit join expressions
+				 * like INNER JOIN, NATURAL JOIN, ...
+				 */
+				return NULL;
+			}
+		}
+		else
+		{
+			/* e.g. SELECT ... FROM rel1, rel2. */
+			Assert(list_length(joinTree->fromlist) > 1);
 			return NULL;
 		}
 #else
+
+		/* query has a FROM section */
 		return NULL;
 #endif
 	}

src/test/regress/expected/multi_mx_call.out

@@ -342,13 +342,12 @@ DETAIL:  A distributed function is created. To make sure subsequent commands see
  
 (1 row)
 
+\set VERBOSITY terse
 call multi_mx_call.mx_call_proc_raise(2);
 DEBUG:  pushing down the procedure
 DEBUG:  warning
-DETAIL:  WARNING from localhost:57638
 ERROR:  error
-CONTEXT:  while executing command on localhost:57638
+\set VERBOSITY default
-PL/pgSQL function multi_mx_call.mx_call_proc_raise(integer) line 4 at RAISE
 -- Test that we don't propagate to non-metadata worker nodes
 select stop_metadata_sync_to_node('localhost', :worker_1_port);
  stop_metadata_sync_to_node 

src/test/regress/expected/multi_mx_call_0.out

@@ -263,10 +263,10 @@ select create_distributed_function('mx_call_proc_raise(int)', '$1', 'mx_call_dis
 ERROR:  function "mx_call_proc_raise(int)" does not exist
 LINE 1: select create_distributed_function('mx_call_proc_raise(int)'...
                                            ^
+\set VERBOSITY terse
 call multi_mx_call.mx_call_proc_raise(2);
-ERROR:  syntax error at or near "call"
+ERROR:  syntax error at or near "call" at character 1
-LINE 1: call multi_mx_call.mx_call_proc_raise(2);
+\set VERBOSITY default
-        ^
 -- Test that we don't propagate to non-metadata worker nodes
 select stop_metadata_sync_to_node('localhost', :worker_1_port);
  stop_metadata_sync_to_node 

src/test/regress/expected/multi_unsupported_worker_operations.out

@@ -265,11 +265,11 @@ SELECT worker_drop_distributed_table(logicalrelid::regclass::text) FROM pg_dist_
 DELETE FROM pg_dist_node;
 \c - - - :worker_1_port
 -- DROP TABLE
+-- terse verbosity because pg10 has slightly different output
+\set VERBOSITY terse
 DROP TABLE mx_table;
 ERROR:  operation is not allowed on this node
-HINT:  Connect to the coordinator and run it again.
+\set VERBOSITY default
-CONTEXT:  SQL statement "SELECT master_remove_distributed_table_metadata_from_workers(v_obj.objid, v_obj.schema_name, v_obj.object_name)"
-PL/pgSQL function citus_drop_trigger() line 18 at PERFORM
 SELECT count(*) FROM mx_table;
  count 
 -------

src/test/regress/sql/multi_mx_call.sql

@@ -143,8 +143,9 @@ BEGIN
     RAISE EXCEPTION 'error';
 END;$$;
 select create_distributed_function('mx_call_proc_raise(int)', '$1', 'mx_call_dist_table_1');
+\set VERBOSITY terse
 call multi_mx_call.mx_call_proc_raise(2);
-
+\set VERBOSITY default
 
 -- Test that we don't propagate to non-metadata worker nodes
 select stop_metadata_sync_to_node('localhost', :worker_1_port);

src/test/regress/sql/multi_unsupported_worker_operations.sql

@@ -154,7 +154,10 @@ DELETE FROM pg_dist_node;
 \c - - - :worker_1_port
 
 -- DROP TABLE
+-- terse verbosity because pg10 has slightly different output
+\set VERBOSITY terse
 DROP TABLE mx_table;
+\set VERBOSITY default
 SELECT count(*) FROM mx_table;
 
 -- master_drop_distributed_table_metadata