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Commit07746a8

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Finish incomplete revert ofec63622.
The code change this made might well be fine to keep, but thecomment justifying it by reference to self-join removal isn't.Let's just go back to the status quo ante, pending a more thoroughreview/redesign of SJE.(I found this by grepping to see if any references to self-joinremoval remained in the tree.)
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‎src/backend/optimizer/prep/prepunion.c

Lines changed: 3 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -662,17 +662,14 @@ build_setop_child_paths(PlannerInfo *root, RelOptInfo *rel,
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* otherwise do statistical estimation.
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*
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* XXX you don't really want to know about this: we do the estimation
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* using thesubroot->parse's original targetlist expressions, not the
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* using thesubquery's original targetlist expressions, not the
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* subroot->processed_tlist which might seem more appropriate. The reason
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* is that if the subquery is itself a setop, it may return a
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* processed_tlist containing "varno 0" Vars generated by
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* generate_append_tlist, and those would confuse estimate_num_groups
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* mightily. We ought to get rid of the "varno 0" hack, but that requires
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* a redesign of the parsetree representation of setops, so that there can
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* be an RTE corresponding to each setop's output. Note, we use this not
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* subquery's targetlist but subroot->parse's targetlist, because it was
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* revised by self-join removal. subquery's targetlist might contain the
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* references to the removed relids.
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* be an RTE corresponding to each setop's output.
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*/
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if (pNumGroups)
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{
@@ -685,7 +682,7 @@ build_setop_child_paths(PlannerInfo *root, RelOptInfo *rel,
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*pNumGroups=rel->cheapest_total_path->rows;
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else
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*pNumGroups=estimate_num_groups(subroot,
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get_tlist_exprs(subroot->parse->targetList, false),
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get_tlist_exprs(subquery->targetList, false),
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rel->cheapest_total_path->rows,
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NULL,
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NULL);

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