Pass additional arguments to a couple of grouping-related functions.

get_number_of_groups() and make_partial_grouping_target() currently
fish information directly out of the PlannerInfo; in the former case,
the target list, and in the latter case, the HAVING qual.  This works
fine if there's only one grouping relation, but if the pending patch
for partition-wise aggregate gets committed, we'll have multiple
grouping relations and must therefore use appropriately translated
versions of these values for each one.  To make that simpler, pass the
values to be used as arguments.

Jeevan Chalke.  The larger patch series of which this patch is a part
was also reviewed and tested by Antonin Houska, Rajkumar Raghuwanshi,
David Rowley, Dilip Kumar, Konstantin Knizhnik, Pascal Legrand, Rafia
Sabih, and me.

Discussion: http://postgr.es/m/CAM2+6=UqFnFUypOvLdm5TgC+2M=-E0Q7_LOh0VDFFzmk2BBPzQ@mail.gmail.com
Discussion: http://postgr.es/m/CAM2+6=W+L=C4yBqMrgrfTfNtbtmr4T53-hZhwbA2kvbZ9VMrrw@mail.gmail.com

src/backend/optimizer/plan/planner.c

@@ -130,7 +130,8 @@ static List *reorder_grouping_sets(List *groupingSets, List *sortclause);
 static void standard_qp_callback(PlannerInfo *root, void *extra);
 static double get_number_of_groups(PlannerInfo *root,
 					 double path_rows,
-					 grouping_sets_data *gd);
+					 grouping_sets_data *gd,
+					 List *target_list);
 static Size estimate_hashagg_tablesize(Path *path,
 						   const AggClauseCosts *agg_costs,
 						   double dNumGroups);
@@ -175,7 +176,8 @@ static RelOptInfo *create_ordered_paths(PlannerInfo *root,
 static PathTarget *make_group_input_target(PlannerInfo *root,
 						PathTarget *final_target);
 static PathTarget *make_partial_grouping_target(PlannerInfo *root,
-							 PathTarget *grouping_target);
+							 PathTarget *grouping_target,
+							 Node *havingQual);
 static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
 static List *select_active_windows(PlannerInfo *root, WindowFuncLists *wflists);
 static PathTarget *make_window_input_target(PlannerInfo *root,
@@ -3505,6 +3507,7 @@ standard_qp_callback(PlannerInfo *root, void *extra)
  *
  * path_rows: number of output rows from scan/join step
  * gd: grouping sets data including list of grouping sets and their clauses
+ * target_list: target list containing group clause references
  *
  * If doing grouping sets, we also annotate the gsets data with the estimates
  * for each set and each individual rollup list, with a view to later
@@ -3513,7 +3516,8 @@ standard_qp_callback(PlannerInfo *root, void *extra)
 static double
 get_number_of_groups(PlannerInfo *root,
 					 double path_rows,
-					 grouping_sets_data *gd)
+					 grouping_sets_data *gd,
+					 List *target_list)
 {
 	Query	   *parse = root->parse;
 	double		dNumGroups;
@@ -3538,7 +3542,7 @@ get_number_of_groups(PlannerInfo *root,
 				ListCell   *lc;
 
 				groupExprs = get_sortgrouplist_exprs(rollup->groupClause,
-													 parse->targetList);
+													 target_list);
 
 				rollup->numGroups = 0.0;
 
@@ -3565,7 +3569,7 @@ get_number_of_groups(PlannerInfo *root,
 				gd->dNumHashGroups = 0;
 
 				groupExprs = get_sortgrouplist_exprs(parse->groupClause,
-													 parse->targetList);
+													 target_list);
 
 				forboth(lc, gd->hash_sets_idx, lc2, gd->unsortable_sets)
 				{
@@ -3587,7 +3591,7 @@ get_number_of_groups(PlannerInfo *root,
 		{
 			/* Plain GROUP BY */
 			groupExprs = get_sortgrouplist_exprs(parse->groupClause,
-												 parse->targetList);
+												 target_list);
 
 			dNumGroups = estimate_num_groups(root, groupExprs, path_rows,
 											 NULL);
@@ -3797,7 +3801,8 @@ create_grouping_paths(PlannerInfo *root,
 	 */
 	dNumGroups = get_number_of_groups(root,
 									  cheapest_path->rows,
-									  gd);
+									  gd,
+									  parse->targetList);
 
 	/*
 	 * Determine whether it's possible to perform sort-based implementations
@@ -3859,7 +3864,8 @@ create_grouping_paths(PlannerInfo *root,
 		 * appear in the result tlist, and (2) the Aggrefs must be set in
 		 * partial mode.
 		 */
-		partial_grouping_target = make_partial_grouping_target(root, target);
+		partial_grouping_target = make_partial_grouping_target(root, target,
+															   (Node *) parse->havingQual);
 		partially_grouped_rel->reltarget = partial_grouping_target;
 
 		/*
@@ -4912,10 +4918,12 @@ make_group_input_target(PlannerInfo *root, PathTarget *final_target)
  * these would be Vars that are grouped by or used in grouping expressions.)
  *
  * grouping_target is the tlist to be emitted by the topmost aggregation step.
- * We get the HAVING clause out of *root.
+ * havingQual represents the HAVING clause.
  */
 static PathTarget *
-make_partial_grouping_target(PlannerInfo *root, PathTarget *grouping_target)
+make_partial_grouping_target(PlannerInfo *root,
+							 PathTarget *grouping_target,
+							 Node *havingQual)
 {
 	Query	   *parse = root->parse;
 	PathTarget *partial_target;
@@ -4957,8 +4965,8 @@ make_partial_grouping_target(PlannerInfo *root, PathTarget *grouping_target)
 	/*
 	 * If there's a HAVING clause, we'll need the Vars/Aggrefs it uses, too.
 	 */
-	if (parse->havingQual)
-		non_group_cols = lappend(non_group_cols, parse->havingQual);
+	if (havingQual)
+		non_group_cols = lappend(non_group_cols, havingQual);
 
 	/*
 	 * Pull out all the Vars, PlaceHolderVars, and Aggrefs mentioned in
@@ -6283,7 +6291,8 @@ add_paths_to_partial_grouping_rel(PlannerInfo *root,
 	/* Estimate number of partial groups. */
 	dNumPartialGroups = get_number_of_groups(root,
 											 cheapest_partial_path->rows,
-											 gd);
+											 gd,
+											 parse->targetList);
 
 	if (can_sort)
 	{