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| author | Alexander Korotkov <akorotkov@postgresql.org> | 2023-11-04 03:30:18 +0200 |
|---|---|---|
| committer | Alexander Korotkov <akorotkov@postgresql.org> | 2023-11-04 03:30:18 +0200 |
| commit | ec63622c03ff7be36d32c08aaa7d853856451488 (patch) | |
| tree | a43f0a94c18fdf23a5890348493b6b3ab484c450 /src/backend/optimizer/prep | |
| parent | a237a07d5351d7bb0afc6e0c41410d52915e47c8 (diff) | |
Fix usage of the parse tree for estimate_num_groups() in set operations
recurse_set_operations() uses the parse tree for the group number estimation,
because of the "varno 0" hack. At the same time 2489d76c49 made root->parse
and corresponding parent_root->simple_rte_array[]->subquery distinct copies
of the parse tree, while d3d55ce571 introduced self-join removal replacing
relid of removed relation only in one of the copies.
The present commit fixes this bug by making recurse_set_operations() call
estimate_num_groups() with the copy of the parse tree processed by self-join
removal.
In future, we may think about maintaining just one copy of the parse tree
and/or keeping removed relids as aliases.
Reported-by: Zuming Jiang
Bug: #18170
Discussion: https://postgr.es/m/flat/18170-f1d17bf9a0d58b24%40postgresql.org
Author: Richard Guo, Alexander Korotkov
Reviewed-by: Andrei Lepikhov
Diffstat (limited to 'src/backend/optimizer/prep')
| -rw-r--r-- | src/backend/optimizer/prep/prepunion.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c index 0c68ec011be..8eaa734916d 100644 --- a/src/backend/optimizer/prep/prepunion.c +++ b/src/backend/optimizer/prep/prepunion.c @@ -324,7 +324,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root, * anyway; otherwise do statistical estimation. * * XXX you don't really want to know about this: we do the estimation - * using the subquery's original targetlist expressions, not the + * using the subroot->parse's original targetlist expressions, not the * subroot->processed_tlist which might seem more appropriate. The * reason is that if the subquery is itself a setop, it may return a * processed_tlist containing "varno 0" Vars generated by @@ -332,6 +332,9 @@ recurse_set_operations(Node *setOp, PlannerInfo *root, * mightily. We ought to get rid of the "varno 0" hack, but that * requires a redesign of the parsetree representation of setops, so * that there can be an RTE corresponding to each setop's output. + * Note, we use this not subquery's targetlist but subroot->parse's + * targetlist, because it was revised by self-join removal. subquery's + * targetlist might contain the references to the removed relids. */ if (pNumGroups) { @@ -341,7 +344,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root, *pNumGroups = subpath->rows; else *pNumGroups = estimate_num_groups(subroot, - get_tlist_exprs(subquery->targetList, false), + get_tlist_exprs(subroot->parse->targetList, false), subpath->rows, NULL, NULL); |