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Commit3d69efc

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Build EC members for child join rels in the right memory context.
This patch prevents crashes or wrong plans when partition-wise joinsare considered during GEQO planning, as a consequence of theEquivalenceClass data structures becoming corrupt after a GEQOcontext reset.A remaining problem is that successive GEQO cycles will make multiplecopies of the required EC members, since add_child_join_rel_equivalenceshas no idea that such members might exist already. For now we'll justlive with that. The lack of field complaints of crashes suggests thatthis is a mighty little-used situation.Back-patch to v12 where this code was introduced.Discussion:https://postgr.es/m/1683100.1601860653@sss.pgh.pa.us
1 parent9b8e685 commit3d69efc

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‎src/backend/optimizer/path/equivclass.c

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@@ -2234,10 +2234,21 @@ add_child_join_rel_equivalences(PlannerInfo *root,
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{
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Relidstop_parent_relids=child_joinrel->top_parent_relids;
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Relidschild_relids=child_joinrel->relids;
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MemoryContextoldcontext;
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ListCell*lc1;
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Assert(IS_JOIN_REL(child_joinrel)&&IS_JOIN_REL(parent_joinrel));
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/*
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* If we're being called during GEQO join planning, we still have to
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* create any new EC members in the main planner context, to avoid having
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* a corrupt EC data structure after the GEQO context is reset. This is
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* problematic since we'll leak memory across repeated GEQO cycles. For
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* now, though, bloat is better than crash. If it becomes a real issue
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* we'll have to do something to avoid generating duplicate EC members.
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*/
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oldcontext=MemoryContextSwitchTo(root->planner_cxt);
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foreach(lc1,root->eq_classes)
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{
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EquivalenceClass*cur_ec= (EquivalenceClass*)lfirst(lc1);
@@ -2334,6 +2345,8 @@ add_child_join_rel_equivalences(PlannerInfo *root,
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}
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}
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}
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MemoryContextSwitchTo(oldcontext);
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}
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