[BACKPORT 2.20.1][#19694] YSQL: Missing finalize_primnode calls

Summary:
Original commit: 5875a24 / D29710
The finalize_plan function in subselect.c basically collects and
summarizes information about parameter references in the subplan.

It calls finalize_primnode to recursively process all possible
containers where Param nodes may be found. We introduced PushdownExprs,
where qual list may contain Param expression, but we didn't update the
finalize_plan function to call finalize_primnode on them.

The only known manifestation is Parallel Query where Gather node does
not transfer parameter values to and from background workers.
Jira: DB-8494

Test Plan: Run regression tests

Reviewers: jason, tnayak

Reviewed By: jason, tnayak

Subscribers: smishra, yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D31303

src/postgres/src/backend/optimizer/plan/subselect.c

@@ -2033,7 +2033,12 @@ finalize_plan(PlannerInfo *root, Plan *plan,
 			break;
 
 		case T_SeqScan:
+			context.paramids = bms_add_members(context.paramids, scan_params);
+			break;
+
 		case T_YbSeqScan:
+			finalize_primnode((Node *) ((YbSeqScan *) plan)->yb_pushdown.quals,
+							  &context);
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
@@ -2048,6 +2053,10 @@ finalize_plan(PlannerInfo *root, Plan *plan,
 							  &context);
 			finalize_primnode((Node *) ((IndexScan *) plan)->indexorderby,
 							  &context);
+			finalize_primnode((Node *) ((IndexScan *) plan)->yb_rel_pushdown.quals,
+							  &context);
+			finalize_primnode((Node *) ((IndexScan *) plan)->yb_idx_pushdown.quals,
+							  &context);
 
 			/*
 			 * we need not look at indexqualorig, since it will have the same
@@ -2062,6 +2071,8 @@ finalize_plan(PlannerInfo *root, Plan *plan,
 							  &context);
 			finalize_primnode((Node *) ((IndexOnlyScan *) plan)->indexorderby,
 							  &context);
+			finalize_primnode((Node *) ((IndexOnlyScan *) plan)->yb_pushdown.quals,
+							  &context);
 
 			/*
 			 * we need not look at indextlist, since it cannot contain Params.