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commit    4169850f0b6fc98a5f28d2b0ca4c3a4c1ecf4553
Author:   David Rowley <drowley@postgresql.org>
Date:     Thu Mar 14 22:54:36 2024 +0000
First released in: 17.0, 16.3

    Trim ORDER BY/DISTINCT aggregate pathkeys in gather_grouping_paths
    
    Similar to d8a295389, trim off any PathKeys which are for ORDER BY /
    DISTINCT aggregate functions from the PathKey List for the Gather Merge
    paths created by gather_grouping_paths().  These additional PathKeys are
    not valid to use after grouping has taken place as these PathKeys belong
    to columns which are inputs to an aggregate function and, therefore are
    unavailable after aggregation.
    
    Reported-by: Alexander Lakhin
    Discussion: https://postgr.es/m/cf63174c-8c89-3953-cb49-48f41f74941a@gmail.com
    Backpatch-through: 16, where 1349d2790 was added


 src/backend/optimizer/plan/planner.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 443ab08d75a..5564826cb4a 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -7320,6 +7320,17 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
 {
 	ListCell   *lc;
 	Path	   *cheapest_partial_path;
+	List	   *groupby_pathkeys;
+
+	/*
+	 * This occurs after any partial aggregation has taken place, so trim off
+	 * any pathkeys added for ORDER BY / DISTINCT aggregates.
+	 */
+	if (list_length(root->group_pathkeys) > root->num_groupby_pathkeys)
+		groupby_pathkeys = list_copy_head(root->group_pathkeys,
+										  root->num_groupby_pathkeys);
+	else
+		groupby_pathkeys = root->group_pathkeys;
 
 	/* Try Gather for unordered paths and Gather Merge for ordered ones. */
 	generate_useful_gather_paths(root, rel, true);
@@ -7334,7 +7345,7 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
 		int			presorted_keys;
 		double		total_groups;
 
-		is_sorted = pathkeys_count_contained_in(root->group_pathkeys,
+		is_sorted = pathkeys_count_contained_in(groupby_pathkeys,
 												path->pathkeys,
 												&presorted_keys);
 
@@ -7360,13 +7371,13 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
 		 */
 		if (presorted_keys == 0 || !enable_incremental_sort)
 			path = (Path *) create_sort_path(root, rel, path,
-											 root->group_pathkeys,
+											 groupby_pathkeys,
 											 -1.0);
 		else
 			path = (Path *) create_incremental_sort_path(root,
 														 rel,
 														 path,
-														 root->group_pathkeys,
+														 groupby_pathkeys,
 														 presorted_keys,
 														 -1.0);
 
@@ -7375,7 +7386,7 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
 									 rel,
 									 path,
 									 rel->reltarget,
-									 root->group_pathkeys,
+									 groupby_pathkeys,
 									 NULL,
 									 &total_groups);
 


[parent: 4665cebc8a01]