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Fix two latent(?) bugs in equivclass.c.

get_eclass_for_sort_expr() computes expr_relids and nullable_relidsearly on, even though they won't be needed unless we make a newEquivalenceClass, which we often don't. Aside from the probably-minorinefficiency, there's a memory management problem: these bitmapsets willbe built in the caller's context, leading to dangling pointers if thatis shorter-lived than root->planner_cxt. This would be a live bug ifget_eclass_for_sort_expr() could be called with create_it = true duringGEQO join planning. So far as I can find, the core code never doesthat, but it's hard to be sure that no extensions do, especially sincethe comments make it clear that that's supposed to be a supported case.Fix by not computing these values until we've switched into planner_cxtto build the new EquivalenceClass.generate_join_implied_equalities() uses inner_rel->relids to look uprelevant eclasses, but it ought to be using nominal_inner_relids.This is presently harmless because a child RelOptInfo will always haveexactly the same eclass_indexes as its topmost parent; but that mightnot be true forever, and anyway it makes the code confusing.The first of these is old (introduced by me inf3b3b8d), so back-patchto all supported branches. The second only dates to v13, but we mightas well back-patch it to keep the code looking similar across branches.Discussion:https://postgr.es/m/1508010.1601832581@sss.pgh.pa.us

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src/backend/optimizer/path
- equivclass.c

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`‎src/backend/optimizer/path/equivclass.c`

Lines changed: 6 additions & 6 deletions

Original file line number	Diff line number	Diff line change
`@@ -600,12 +600,6 @@ get_eclass_for_sort_expr(PlannerInfo *root,`
`600`	`600`	`*/`
`601`	`601`	`expr=canonicalize_ec_expression(expr,opcintype,collation);`
`602`	`602`
`603`		`-/*`
`604`		`- * Get the precise set of nullable relids appearing in the expression.`
`605`		`- */`
`606`		`-expr_relids=pull_varnos((Node*)expr);`
`607`		`-nullable_relids=bms_intersect(nullable_relids,expr_relids);`
`608`		`-`
`609`	`603`	`/*`
`610`	`604`	`* Scan through the existing EquivalenceClasses for a match`
`611`	`605`	`*/`
`@@ -682,6 +676,12 @@ get_eclass_for_sort_expr(PlannerInfo *root,`
`682`	`676`	`if (newec->ec_has_volatile&&sortref==0)/* should not happen */`
`683`	`677`	`elog(ERROR,"volatile EquivalenceClass has no sortref");`
`684`	`678`
	`679`	`+/*`
	`680`	`+ * Get the precise set of nullable relids appearing in the expression.`
	`681`	`+ */`
	`682`	`+expr_relids=pull_varnos((Node*)expr);`
	`683`	`+nullable_relids=bms_intersect(nullable_relids,expr_relids);`
	`684`	`+`
`685`	`685`	`newem=add_eq_member(newec,copyObject(expr),expr_relids,`
`686`	`686`	`nullable_relids, false,opcintype);`
`687`	`687`

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`‎src/backend/optimizer/path/equivclass.c`

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