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authorTom Lane2022-07-30 17:05:15 +0000
committerTom Lane2022-07-30 17:05:15 +0000
commitd8e34fa7a18fab4aa8eb010edac133d63ecc11c6 (patch)
treed9934332e1ff2c3e86df071f42131133432f8ca9
parentd10fad96c664a503a4203fc4b5acd4e816b0158a (diff)
Fix incorrect is-this-the-topmost-join tests in parallel planning.
Two callers of generate_useful_gather_paths were testing the wrong thing when deciding whether to call that function: they checked for being at the top of the current join subproblem, rather than being at the actual top join. This'd result in failing to construct parallel paths for a sub-join for which they might be useful. While set_rel_pathlist() isn't actively broken, it seems best to make its identical-in-intention test for this be like the other two. This has been wrong all along, but given the lack of field complaints I'm hesitant to back-patch into stable branches; we usually prefer to avoid non-bug-fix changes in plan choices in minor releases. It seems not too late for v15 though. Richard Guo, reviewed by Antonin Houska and Tom Lane Discussion: https://postgr.es/m/CAMbWs4-mH8Zf87-w+3P2J=nJB+5OyicO28ia9q_9o=Lamf_VHg@mail.gmail.com
-rw-r--r--src/backend/optimizer/geqo/geqo_eval.c2
-rw-r--r--src/backend/optimizer/path/allpaths.c9
2 files changed, 5 insertions, 6 deletions
diff --git a/src/backend/optimizer/geqo/geqo_eval.c b/src/backend/optimizer/geqo/geqo_eval.c
index de695c0a789..004481d6082 100644
--- a/src/backend/optimizer/geqo/geqo_eval.c
+++ b/src/backend/optimizer/geqo/geqo_eval.c
@@ -273,7 +273,7 @@ merge_clump(PlannerInfo *root, List *clumps, Clump *new_clump, int num_gene,
* rel once we know the final targetlist (see
* grouping_planner).
*/
- if (old_clump->size + new_clump->size < num_gene)
+ if (!bms_equal(joinrel->relids, root->all_baserels))
generate_useful_gather_paths(root, joinrel, false);
/* Find and save the cheapest paths for this joinrel */
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 63f0f6b79c7..b23cc8ee82d 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -554,12 +554,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
* its own pool of workers. Instead, we'll consider gathering partial
* paths for the parent appendrel.
*
- * Also, if this is the topmost scan/join rel (that is, the only baserel),
- * we postpone gathering until the final scan/join targetlist is available
- * (see grouping_planner).
+ * Also, if this is the topmost scan/join rel, we postpone gathering until
+ * the final scan/join targetlist is available (see grouping_planner).
*/
if (rel->reloptkind == RELOPT_BASEREL &&
- bms_membership(root->all_baserels) != BMS_SINGLETON)
+ !bms_equal(rel->relids, root->all_baserels))
generate_useful_gather_paths(root, rel, false);
/* Now find the cheapest of the paths for this rel */
@@ -3435,7 +3434,7 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
* partial paths. We'll do the same for the topmost scan/join rel
* once we know the final targetlist (see grouping_planner).
*/
- if (lev < levels_needed)
+ if (!bms_equal(rel->relids, root->all_baserels))
generate_useful_gather_paths(root, rel, false);
/* Find and save the cheapest paths for this rel */