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Commit1f91c8c

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Avoid planner crash/Assert failure with joins to unflattened subqueries.
examine_simple_variable supposed that any RTE_SUBQUERY rel it gets pointedat must have been planned already. However, this isn't a safe assumptionbecause we must do selectivity estimation while generating indexscan paths,and that code might look at join clauses involving a rel that the loop inset_base_rel_sizes() hasn't reached yet. The simplest fix is to play dumbin such a situation, that is give up trying to extract any stats for theVar. This could possibly be improved by making a separate pass over theRTE list to plan each unflattened subquery before we start the mainplanning work --- but that would be pretty invasive and it doesn't seemworth it, for now at least. (We couldn't just break set_base_rel_sizes()into two loops: the prescan would need to handle all subquery rels in thequery, not only those in the current join subproblem.)This bug was introduced in commit1cb108e,although I think that subsequent changes may have exposed it more than itwas originally. Per bug #7580 from Maxim Boguk.
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‎src/backend/utils/adt/selfuncs.c

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -4518,8 +4518,10 @@ examine_simple_variable(PlannerInfo *root, Var *var,
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*/
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rel=find_base_rel(root,var->varno);
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/* Subquery should have been planned already */
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Assert(rel->subroot&&IsA(rel->subroot,PlannerInfo));
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/* If the subquery hasn't been planned yet, we have to punt */
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if (rel->subroot==NULL)
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return;
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Assert(IsA(rel->subroot,PlannerInfo));
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/*
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* Switch our attention to the subquery as mangled by the planner. It

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