Delegate function calls in FROM outside of transaction block

src/backend/distributed/planner/function_call_delegation.c

@@ -313,16 +313,6 @@ TryToDelegateFunctionCall(DistributedPlanningContext *planContext)
 		return NULL;
 	}
 
-	if (fromFuncExpr && !IsMultiStatementTransaction())
-	{
-		/*
-		 * For now, let's not push the function from the FROM clause unless it's in a
-		 * multistatement transaction with the forceDelegation flag ON.
-		 */
-		ereport(DEBUG2, (errmsg("function from the FROM clause is not pushed")));
-		return NULL;
-	}
-
 	/* dissuade the planner from trying a generic plan with parameters */
 	(void) expression_tree_walker((Node *) funcExpr->args, contain_param_walker,
 								  &walkerParamContext);

src/test/regress/expected/forcedelegation_functions.out

@@ -1162,18 +1162,11 @@ SELECT * FROM forcepushdown_schema.test_subquery ORDER BY 1;
 (5 rows)
 
 -- Query with targetList greater than 1
--- Function from FROM clause is not delegated outside of a BEGIN (for now)
+-- Function from FROM clause is delegated outside of a BEGIN
 SELECT 1,2,3 FROM select_data(100);
-DEBUG:  generating subplan XXX_1 for subquery SELECT data FROM forcepushdown_schema.test_subquery WHERE (data OPERATOR(pg_catalog.=) 100)
+DEBUG:  pushing down the function call
-CONTEXT:  SQL statement "SELECT result          FROM forcepushdown_schema.test_subquery WHERE data =
-		(SELECT data FROM forcepushdown_schema.test_subquery WHERE data = a)"
-PL/pgSQL function select_data(integer) line XX at SQL statement
-DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT result FROM forcepushdown_schema.test_subquery WHERE (data OPERATOR(pg_catalog.=) (SELECT intermediate_result.data FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(data integer)))
-CONTEXT:  SQL statement "SELECT result          FROM forcepushdown_schema.test_subquery WHERE data =
-		(SELECT data FROM forcepushdown_schema.test_subquery WHERE data = a)"
-PL/pgSQL function select_data(integer) line XX at SQL statement
 NOTICE:  Result: -1
-CONTEXT:  PL/pgSQL function select_data(integer) line XX at RAISE
+DETAIL:  from localhost:xxxxx
  ?column? | ?column? | ?column?
 ---------------------------------------------------------------------
         1 |        2 |        3

src/test/regress/expected/multi_mx_function_call_delegation.out

@@ -630,18 +630,6 @@ PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
 (1 row)
 
 -- test forms we don't distribute
-select * from mx_call_func(2, 0);
-DEBUG:  generating subplan XXX_1 for subquery SELECT sum((t1.val OPERATOR(pg_catalog.+) t2.val)) AS sum FROM (multi_mx_function_call_delegation.mx_call_dist_table_1 t1 JOIN multi_mx_function_call_delegation.mx_call_dist_table_2 t2 ON ((t1.id OPERATOR(pg_catalog.=) t2.id)))
-CONTEXT:  PL/pgSQL assignment "y := y + (select sum(t1.val + t2.val) from multi_mx_function_call_delegation.mx_call_dist_table_1 t1 join multi_mx_function_call_delegation.mx_call_dist_table_2 t2 on t1.id = t2.id)"
-PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
-DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT ((3 OPERATOR(pg_catalog.+) (SELECT intermediate_result.sum FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(sum bigint))))::integer
-CONTEXT:  PL/pgSQL assignment "y := y + (select sum(t1.val + t2.val) from multi_mx_function_call_delegation.mx_call_dist_table_1 t1 join multi_mx_function_call_delegation.mx_call_dist_table_2 t2 on t1.id = t2.id)"
-PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
- y
----------------------------------------------------------------------
- 29
-(1 row)
-
 select mx_call_func(2, 0) where mx_call_func(0, 2) = 0;
 DEBUG:  generating subplan XXX_1 for subquery SELECT sum((t1.val OPERATOR(pg_catalog.+) t2.val)) AS sum FROM (multi_mx_function_call_delegation.mx_call_dist_table_1 t1 JOIN multi_mx_function_call_delegation.mx_call_dist_table_2 t2 ON ((t1.id OPERATOR(pg_catalog.=) t2.id)))
 CONTEXT:  PL/pgSQL assignment "y := y + (select sum(t1.val + t2.val) from multi_mx_function_call_delegation.mx_call_dist_table_1 t1 join multi_mx_function_call_delegation.mx_call_dist_table_2 t2 on t1.id = t2.id)"
@@ -671,6 +659,58 @@ PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
            29 |           27
 (1 row)
 
+-- regular call in FROM can be pushed down
+select * from mx_call_func(2, 0);
+DEBUG:  pushing down the function call
+ y
+---------------------------------------------------------------------
+ 28
+(1 row)
+
+-- prepared statement with 6 invocations to trigger generic plan
+prepare call_func(int, int) as select $1 from mx_call_func($1, $2);
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
 -- we do not delegate the call, but do push down the query
 -- that result in remote execution from workers
 select mx_call_func(id, 0) from mx_call_dist_table_1;

src/test/regress/expected/multi_mx_function_call_delegation_0.out

@@ -630,18 +630,6 @@ PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
 (1 row)
 
 -- test forms we don't distribute
-select * from mx_call_func(2, 0);
-DEBUG:  generating subplan XXX_1 for subquery SELECT sum((t1.val OPERATOR(pg_catalog.+) t2.val)) AS sum FROM (multi_mx_function_call_delegation.mx_call_dist_table_1 t1 JOIN multi_mx_function_call_delegation.mx_call_dist_table_2 t2 ON ((t1.id OPERATOR(pg_catalog.=) t2.id)))
-CONTEXT:  SQL statement "SELECT y + (select sum(t1.val + t2.val) from multi_mx_function_call_delegation.mx_call_dist_table_1 t1 join multi_mx_function_call_delegation.mx_call_dist_table_2 t2 on t1.id = t2.id)"
-PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
-DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT (3 OPERATOR(pg_catalog.+) (SELECT intermediate_result.sum FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(sum bigint)))
-CONTEXT:  SQL statement "SELECT y + (select sum(t1.val + t2.val) from multi_mx_function_call_delegation.mx_call_dist_table_1 t1 join multi_mx_function_call_delegation.mx_call_dist_table_2 t2 on t1.id = t2.id)"
-PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
- y
----------------------------------------------------------------------
- 29
-(1 row)
-
 select mx_call_func(2, 0) where mx_call_func(0, 2) = 0;
 DEBUG:  generating subplan XXX_1 for subquery SELECT sum((t1.val OPERATOR(pg_catalog.+) t2.val)) AS sum FROM (multi_mx_function_call_delegation.mx_call_dist_table_1 t1 JOIN multi_mx_function_call_delegation.mx_call_dist_table_2 t2 ON ((t1.id OPERATOR(pg_catalog.=) t2.id)))
 CONTEXT:  SQL statement "SELECT y + (select sum(t1.val + t2.val) from multi_mx_function_call_delegation.mx_call_dist_table_1 t1 join multi_mx_function_call_delegation.mx_call_dist_table_2 t2 on t1.id = t2.id)"
@@ -671,6 +659,58 @@ PL/pgSQL function mx_call_func(integer,integer) line XX at assignment
            29 |           27
 (1 row)
 
+-- regular call in FROM can be pushed down
+select * from mx_call_func(2, 0);
+DEBUG:  pushing down the function call
+ y
+---------------------------------------------------------------------
+ 28
+(1 row)
+
+-- prepared statement with 6 invocations to trigger generic plan
+prepare call_func(int, int) as select $1 from mx_call_func($1, $2);
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
+execute call_func(2, 0);
+DEBUG:  pushing down the function call
+ ?column?
+---------------------------------------------------------------------
+        2
+(1 row)
+
 -- we do not delegate the call, but do push down the query
 -- that result in remote execution from workers
 select mx_call_func(id, 0) from mx_call_dist_table_1;

src/test/regress/sql/forcedelegation_functions.sql

@@ -606,8 +606,9 @@ SELECT * FROM forcepushdown_schema.test_subquery ORDER BY 1;
 
 -- Query with targetList greater than 1
 
--- Function from FROM clause is not delegated outside of a BEGIN (for now)
+-- Function from FROM clause is delegated outside of a BEGIN
 SELECT 1,2,3 FROM select_data(100);
+
 BEGIN;
 -- Function from FROM clause is delegated
 SELECT 1,2,3 FROM select_data(100);

src/test/regress/sql/multi_mx_function_call_delegation.sql

@@ -274,10 +274,21 @@ select mx_call_func((select x + 1 from mx_call_add(3, 4) x), 2);
 select mx_call_func(floor(random())::int, 2);
 
 -- test forms we don't distribute
-select * from mx_call_func(2, 0);
 select mx_call_func(2, 0) where mx_call_func(0, 2) = 0;
 select mx_call_func(2, 0), mx_call_func(0, 2);
 
+-- regular call in FROM can be pushed down
+select * from mx_call_func(2, 0);
+
+-- prepared statement with 6 invocations to trigger generic plan
+prepare call_func(int, int) as select $1 from mx_call_func($1, $2);
+execute call_func(2, 0);
+execute call_func(2, 0);
+execute call_func(2, 0);
+execute call_func(2, 0);
+execute call_func(2, 0);
+execute call_func(2, 0);
+
 -- we do not delegate the call, but do push down the query
 -- that result in remote execution from workers
 select mx_call_func(id, 0) from mx_call_dist_table_1;