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| author | Amit Kapila <akapila@postgresql.org> | 2018-09-14 09:36:30 +0530 |
|---|---|---|
| committer | Amit Kapila <akapila@postgresql.org> | 2018-09-14 09:36:30 +0530 |
| commit | 75f9c4ca5a8047d7a9cfbc7d51a610933d04dc7f (patch) | |
| tree | 888a57df088ecaab838f08475d295ace7e30ae67 /src/backend/optimizer/plan/planner.c | |
| parent | 0ba06e0bfb8cfd24ff17aca92aa72245ddd6c4d7 (diff) | |
| download | postgresql-75f9c4ca5a8047d7a9cfbc7d51a610933d04dc7f.tar.gz postgresql-75f9c4ca5a8047d7a9cfbc7d51a610933d04dc7f.zip | |
Don't allow LIMIT/OFFSET clause within sub-selects to be pushed to workers.
Allowing sub-select containing LIMIT/OFFSET in workers can lead to
inconsistent results at the top-level as there is no guarantee that the
row order will be fully deterministic. The fix is to prohibit pushing
LIMIT/OFFSET within sub-selects to workers.
Reported-by: Andrew Fletcher
Bug: 15324
Author: Amit Kapila
Reviewed-by: Dilip Kumar
Backpatch-through: 9.6
Discussion: https://postgr.es/m/153417684333.10284.11356259990921828616@wrigleys.postgresql.org
Diffstat (limited to 'src/backend/optimizer/plan/planner.c')
| -rw-r--r-- | src/backend/optimizer/plan/planner.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 96bf0601a8e..e589471fee8 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -123,7 +123,6 @@ static void preprocess_rowmarks(PlannerInfo *root); static double preprocess_limit(PlannerInfo *root, double tuple_fraction, int64 *offset_est, int64 *count_est); -static bool limit_needed(Query *parse); static void remove_useless_groupby_columns(PlannerInfo *root); static List *preprocess_groupclause(PlannerInfo *root, List *force); static List *extract_rollup_sets(List *groupingSets); @@ -2870,7 +2869,7 @@ preprocess_limit(PlannerInfo *root, double tuple_fraction, * a key distinction: here we need hard constants in OFFSET/LIMIT, whereas * in preprocess_limit it's good enough to consider estimated values. */ -static bool +bool limit_needed(Query *parse) { Node *node; |