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Don't allow LIMIT/OFFSET clause within sub-selects to be pushed to workers.

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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
This commit is contained in:
Amit Kapila
2018-09-14 09:36:30 +05:30
parent 0ba06e0bfb
commit 75f9c4ca5a
5 changed files with 40 additions and 2 deletions
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2
src/include/optimizer/planner.h
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@@ -47,6 +47,8 @@ extern bool is_dummy_plan(Plan *plan);
extern RowMarkType select_rowmark_type(RangeTblEntry *rte,
LockClauseStrength strength);
extern bool limit_needed(Query *parse);
extern void mark_partial_aggref(Aggref *agg, AggSplit aggsplit);
extern Path *get_cheapest_fractional_path(RelOptInfo *rel,