diff options
Diffstat (limited to 'src/backend/optimizer/plan/createplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/createplan.c | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c index 40abe6f9f62..5ecf9f40658 100644 --- a/src/backend/optimizer/plan/createplan.c +++ b/src/backend/optimizer/plan/createplan.c @@ -1793,13 +1793,15 @@ create_gather_merge_plan(PlannerInfo *root, GatherMergePath *best_path) &gm_plan->nullsFirst); - /* Now, insert a Sort node if subplan isn't sufficiently ordered */ + /* + * All gather merge paths should have already guaranteed the necessary sort + * order either by adding an explicit sort node or by using presorted input. + * We can't simply add a sort here on additional pathkeys, because we can't + * guarantee the sort would be safe. For example, expressions may be + * volatile or otherwise parallel unsafe. + */ if (!pathkeys_contained_in(pathkeys, best_path->subpath->pathkeys)) - subplan = (Plan *) make_sort(subplan, gm_plan->numCols, - gm_plan->sortColIdx, - gm_plan->sortOperators, - gm_plan->collations, - gm_plan->nullsFirst); + elog(ERROR, "gather merge input not sufficiently sorted"); /* Now insert the subplan under GatherMerge. */ gm_plan->plan.lefttree = subplan; |