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Commitd7885b1

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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
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‎src/backend/optimizer/path/equivclass.c

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@@ -2380,13 +2380,24 @@ add_child_join_rel_equivalences(PlannerInfo *root,
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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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Bitmapset*matching_ecs;
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MemoryContextoldcontext;
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inti;
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Assert(IS_JOIN_REL(child_joinrel)&&IS_JOIN_REL(parent_joinrel));
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/* We need consider only ECs that mention the parent joinrel */
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matching_ecs=get_eclass_indexes_for_relids(root,top_parent_relids);
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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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i=-1;
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while ((i=bms_next_member(matching_ecs,i)) >=0)
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{
@@ -2486,6 +2497,8 @@ 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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