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Fix partial aggregation for the case of a degenerate GROUP BY clause.

2016年11月10日 16:31:56 +0000 (11:31 -0500)

The plan generated for sorted partial aggregation with "GROUP BY constant"
included a Sort node with no sort keys, which the executor does not like.

Per report from Steve Randall. I'd add a regression test case if I could
think of a compact one, but it doesn't seem worth expending lots of cycles
on.

Report: <CABVd52UAdGXpg_rCk46egpNKYdXOzCjuJ1zG26E2xBe_8bj+Fg@mail.gmail.com>

src/backend/optimizer/plan/planner.c patch | blob | blame | history

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c

index 644b8b6763d6aab7d94a59c6fb65f84be5a6faed..d8c5dd34d6a314a9d229b4dfceb20cf1c3aef82d 100644 (file)

--- a/src/backend/optimizer/plan/planner.c

+++ b/src/backend/optimizer/plan/planner.c

@@ -3741,11 +3741,11 @@ create_grouping_paths(PlannerInfo *root,

&total_groups);

- * Gather is always unsorted, so we'll need to sort, unless

- * there's no GROUP BY clause, in which case there will only be a

- * single group.

+ * Since Gather's output is always unsorted, we'll need to sort,

+ * unless there's no GROUP BY clause or a degenerate (constant)