diff options
Diffstat (limited to 'src/backend/optimizer/prep/prepunion.c')
| -rw-r--r-- | src/backend/optimizer/prep/prepunion.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c index 7c27dc24e21..eab44da65b8 100644 --- a/src/backend/optimizer/prep/prepunion.c +++ b/src/backend/optimizer/prep/prepunion.c @@ -639,14 +639,17 @@ build_setop_child_paths(PlannerInfo *root, RelOptInfo *rel, * 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 * generate_append_tlist, and those would confuse estimate_num_groups * 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. + * 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) { @@ -659,7 +662,7 @@ build_setop_child_paths(PlannerInfo *root, RelOptInfo *rel, *pNumGroups = rel->cheapest_total_path->rows; else *pNumGroups = estimate_num_groups(subroot, - get_tlist_exprs(subquery->targetList, false), + get_tlist_exprs(subroot->parse->targetList, false), rel->cheapest_total_path->rows, NULL, NULL); |