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One of the things canonicalize_qual() does is to remove constant-NULL subexpressions of top-level AND/OR clauses. It does that on the assumption that what it's given is a top-level WHERE clause, so that NULL can be treated like FALSE. Although this is documented down inside a subroutine of canonicalize_qual(), it wasn't mentioned in the documentation of that function itself, and some callers hadn't gotten that memo. Notably, commitd007a9505caused get_relation_constraints() to apply canonicalize_qual() to CHECK constraints. That allowed constraint exclusion to misoptimize situations in which a CHECK constraint had a provably-NULL subclause, as seen in the regression test case added here, in which a child table that should be scanned is not. (Although this thinko is ancient, the test case doesn't fail before 9.2, for reasons I've not bothered to track down in detail. There may be related cases that do fail before that.) More recently, commitf0e44751dadded an independent bug by applying canonicalize_qual() to index expressions, which is even sillier since those might not even be boolean. If they are, though, I think this could lead to making incorrect index entries for affected index expressions in v10. I haven't attempted to prove that though. To fix, add an "is_check" parameter to canonicalize_qual() to specify whether it should assume WHERE or CHECK semantics, and make it perform NULL-elimination accordingly. Adjust the callers to apply the right semantics, or remove the call entirely in cases where it's not known that the expression has one or the other semantics. I also removed the call in some cases involving partition expressions, where it should be a no-op because such expressions should be canonical already ... and was a no-op, independently of whether it could in principle have done something, because it was being handed the qual in implicit-AND format which isn't what it expects. In HEAD, add an Assert to catch that type of mistake in future. This represents an API break for external callers of canonicalize_qual(). While that's intentional in HEAD to make such callers think about which case applies to them, it seems like something we probably wouldn't be thanked for in released branches. Hence, in released branches, the extra parameter is added to a new function canonicalize_qual_ext(), and canonicalize_qual() is a wrapper that retains its old behavior. Patch by me with suggestions from Dean Rasheed. Back-patch to all supported branches. Discussion: https://postgr.es/m/24475.1520635069@sss.pgh.pa.us
69 lines
2.0 KiB
C
69 lines
2.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* prep.h
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* prototypes for files in optimizer/prep/
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*
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*
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* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/optimizer/prep.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PREP_H
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#define PREP_H
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#include "nodes/plannodes.h"
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#include "nodes/relation.h"
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/*
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* prototypes for prepjointree.c
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*/
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extern void pull_up_sublinks(PlannerInfo *root);
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extern void inline_set_returning_functions(PlannerInfo *root);
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extern void pull_up_subqueries(PlannerInfo *root);
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extern void flatten_simple_union_all(PlannerInfo *root);
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extern void reduce_outer_joins(PlannerInfo *root);
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extern Relids get_relids_in_jointree(Node *jtnode, bool include_joins);
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extern Relids get_relids_for_join(PlannerInfo *root, int joinrelid);
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/*
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* prototypes for prepqual.c
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*/
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extern Node *negate_clause(Node *node);
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extern Expr *canonicalize_qual(Expr *qual, bool is_check);
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/*
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* prototypes for preptlist.c
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*/
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extern List *preprocess_targetlist(PlannerInfo *root);
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extern PlanRowMark *get_plan_rowmark(List *rowmarks, Index rtindex);
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/*
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* prototypes for prepunion.c
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*/
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extern RelOptInfo *plan_set_operations(PlannerInfo *root);
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extern void expand_inherited_tables(PlannerInfo *root);
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extern Node *adjust_appendrel_attrs(PlannerInfo *root, Node *node,
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int nappinfos, AppendRelInfo **appinfos);
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extern Node *adjust_appendrel_attrs_multilevel(PlannerInfo *root, Node *node,
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Relids child_relids,
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Relids top_parent_relids);
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extern AppendRelInfo **find_appinfos_by_relids(PlannerInfo *root,
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Relids relids, int *nappinfos);
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extern SpecialJoinInfo *build_child_join_sjinfo(PlannerInfo *root,
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SpecialJoinInfo *parent_sjinfo,
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Relids left_relids, Relids right_relids);
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extern Relids adjust_child_relids_multilevel(PlannerInfo *root, Relids relids,
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Relids child_relids, Relids top_parent_relids);
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#endif /* PREP_H */
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