From ea190ed14b4b75b38a490707d5d08231dcacfb8c Mon Sep 17 00:00:00 2001 From: Tomas Vondra Date: Mon, 21 Dec 2020 18:16:16 +0100 Subject: Consider unsorted paths in generate_useful_gather_paths generate_useful_gather_paths used to skip unsorted paths (without any pathkeys), but that is unnecessary - the later code actually can handle such paths just fine by adding a Sort node. This is clearly a thinko, preventing construction of useful plans. Backpatch to 13, where Incremental Sort was introduced. Author: James Coleman Reviewed-by: Tomas Vondra Backpatch-through: 13 Discussion: https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs=hC0mSksZC=H5M8LSchj5e5OxpTAg@mail.gmail.com --- src/backend/optimizer/path/allpaths.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) (limited to 'src/backend/optimizer/path/allpaths.c') diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 09a0ee24d60..fa2cf61329c 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -2840,7 +2840,8 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r cheapest_partial_path = linitial(rel->partial_pathlist); /* - * Consider incremental sort paths for each interesting ordering. + * Consider sorted paths for each interesting ordering. We generate both + * incremental and full sort. */ foreach(lc, useful_pathkeys_list) { @@ -2854,14 +2855,6 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r Path *subpath = (Path *) lfirst(lc2); GatherMergePath *path; - /* - * If the path has no ordering at all, then we can't use either - * incremental sort or rely on implict sorting with a gather - * merge. - */ - if (subpath->pathkeys == NIL) - continue; - is_sorted = pathkeys_count_contained_in(useful_pathkeys, subpath->pathkeys, &presorted_keys); -- cgit v1.2.3