ADBDEV-6808: Fix initplan functions returning NULL.

src/backend/optimizer/plan/createplan.c

@@ -1970,6 +1970,8 @@ pathtarget_contains_rowidexpr(PathTarget *pathtarget)
 	return false;
 }
 
+static bool is_function_scan_on_initplan(PlannerInfo *root, Path *best_path);
+
 /*
  * create_projection_plan
  *
@@ -2026,8 +2028,8 @@ create_projection_plan(PlannerInfo *root, ProjectionPath *best_path, int flags)
 		 * Tell create_plan_recurse that we're going to ignore the tlist it
 		 * produces.
 		 */
-		subplan = create_plan_recurse(root, best_path->subpath,
-									  CP_IGNORE_TLIST);
+		int subplan_flags = is_function_scan_on_initplan(root, best_path->subpath) ? 0 : CP_IGNORE_TLIST;
+		subplan = create_plan_recurse(root, best_path->subpath, subplan_flags);
 		Assert(is_projection_capable_plan(subplan));
 		tlist = build_path_tlist(root, &best_path->path);
 	}
@@ -8205,6 +8207,65 @@ cdbpathtoplan_create_motion_plan(PlannerInfo *root,
 	return motion;
 }								/* cdbpathtoplan_create_motion_plan */
 
+/*
+ * is_function_scan_on_initplan
+ *
+ * CDB: gpdb specific function to check if a function scan should be executed on an initplan.
+ */
+static bool
+is_function_scan_on_initplan(PlannerInfo *root, Path *best_path) {
+	Index				scan_relid = best_path->parent->relid;
+	RangeTblEntry 	   *rte;
+	RangeTblFunction   *rtfunc;
+	FuncExpr		   *funcexpr;
+	char				exec_location;
+
+	if (best_path->pathtype != T_FunctionScan)
+		return false;
+
+	/*
+	 * In utility mode (or when planning a local query in QE), ignore EXECUTE
+	 * ON markings and run the function the normal way.
+	 */
+	if (Gp_role != GP_ROLE_DISPATCH)
+		return false;
+
+	/* Current function scan is already in an initplan, do nothing. */
+	if (!get_allow_append_initplan_for_function_scan())
+		return false;
+
+	/*
+	 * If INITPLAN function is executed on QD, there is no
+	 * need to add additional initplan to run this function.
+	 * Recall that the reason to introduce INITPLAN function
+	 * is that function runing on QE can not do dispatch.
+	 */
+	if (root->curSlice->parentIndex == -1)
+		return false;
+
+	/* it should be a function base rel... */
+	Assert(scan_relid > 0);
+	rte = planner_rt_fetch(scan_relid, root);
+	Assert(rte->rtekind == RTE_FUNCTION);
+
+	/* Currently we limit function number to one */
+	if (list_length(rte->functions) != 1)
+		return false;
+
+	rtfunc = (RangeTblFunction *) linitial(rte->functions);
+
+	if (!IsA(rtfunc->funcexpr, FuncExpr))
+		return false;
+
+	/* function must be specified EXECUTE ON INITPLAN */
+	funcexpr = (FuncExpr *) rtfunc->funcexpr;
+	exec_location = func_exec_location(funcexpr->funcid);
+	if (exec_location != PROEXECLOCATION_INITPLAN)
+		return false;
+
+	return true;
+}
+
 /*
  * append_initplan_for_function_scan
  *

src/test/regress/expected/function_extensions.out

@@ -577,3 +577,22 @@ select array(select f from hello_initplan() as f);
  {hello}
 (1 row)
 
+-- Test INITPLAN functions with projections
+DROP TABLE IF EXISTS t8_function_scan;
+-- should succeed and add 3 rows with IDs (112, 223, 334)
+CREATE TABLE t8_function_scan AS SELECT country_id+1 AS a, country FROM get_country();
+-- should succeed and add 3 rows with IDs (113, 224, 335)
+INSERT INTO t8_function_scan SELECT country_id+2 AS a, country FROM get_country();
+-- should have 6 rows without any NULL entries
+SELECT * FROM t8_function_scan ORDER BY a;
+  a  | country 
+-----+---------
+ 112 | INDIA
+ 113 | INDIA
+ 223 | CANADA
+ 224 | CANADA
+ 334 | USA
+ 335 | USA
+(6 rows)
+
+DROP TABLE t8_function_scan;

src/test/regress/expected/function_extensions_optimizer.out

@@ -578,3 +578,22 @@ select array(select f from hello_initplan() as f);
  {hello}
 (1 row)
 
+-- Test INITPLAN functions with projections
+DROP TABLE IF EXISTS t8_function_scan;
+-- should succeed and add 3 rows with IDs (112, 223, 334)
+CREATE TABLE t8_function_scan AS SELECT country_id+1 AS a, country FROM get_country();
+-- should succeed and add 3 rows with IDs (113, 224, 335)
+INSERT INTO t8_function_scan SELECT country_id+2 AS a, country FROM get_country();
+-- should have 6 rows without any NULL entries
+SELECT * FROM t8_function_scan ORDER BY a;
+  a  | country 
+-----+---------
+ 112 | INDIA
+ 113 | INDIA
+ 223 | CANADA
+ 224 | CANADA
+ 334 | USA
+ 335 | USA
+(6 rows)
+
+DROP TABLE t8_function_scan;

src/test/regress/sql/function_extensions.sql

@@ -298,5 +298,13 @@ execute on initplan;
 explain select array(select f from hello_initplan() as f);
 select array(select f from hello_initplan() as f);
 
-
+-- Test INITPLAN functions with projections
+DROP TABLE IF EXISTS t8_function_scan;
+-- should succeed and add 3 rows with IDs (112, 223, 334)
+CREATE TABLE t8_function_scan AS SELECT country_id+1 AS a, country FROM get_country();
+-- should succeed and add 3 rows with IDs (113, 224, 335)
+INSERT INTO t8_function_scan SELECT country_id+2 AS a, country FROM get_country();
+-- should have 6 rows without any NULL entries
+SELECT * FROM t8_function_scan ORDER BY a;
+DROP TABLE t8_function_scan;