From 71e58dcfb9ee47064a3ccfeba66a5bdf026380b5 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 12 Oct 2012 12:10:49 -0400 Subject: [PATCH] Make equal() ignore CoercionForm fields for better planning with casts. This change ensures that the planner will see implicit and explicit casts as equivalent for all purposes, except in the minority of cases where there's actually a semantic difference (as reflected by having a 3-argument cast function). In particular, this fixes cases where the EquivalenceClass machinery failed to consider two references to a varchar column as equivalent if one was implicitly cast to text but the other was explicitly cast to text, as seen in bug #7598 from Vaclav Juza. We have had similar bugs before in other parts of the planner, so I think it's time to fix this problem at the core instead of continuing to band-aid around it. Remove set_coercionform_dontcare(), which represents the band-aid previously in use for allowing matching of index and constraint expressions with inconsistent cast labeling. (We can probably get rid of COERCE_DONTCARE altogether, but I don't think removing that enum value in back branches would be wise; it's possible there's third party code referring to it.) Back-patch to 9.2. We could go back further, and might want to once this has been tested more; but for the moment I won't risk destabilizing plan choices in long-since-stable branches. --- src/backend/nodes/equalfuncs.c | 81 ++++------------------------ src/backend/optimizer/util/clauses.c | 42 --------------- src/backend/optimizer/util/plancat.c | 6 --- src/backend/utils/cache/relcache.c | 12 ----- src/include/nodes/primnodes.h | 6 +++ src/include/optimizer/clauses.h | 2 - 6 files changed, 17 insertions(+), 132 deletions(-) diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c index 226b99a1d2..95a95f477b 100644 --- a/src/backend/nodes/equalfuncs.c +++ b/src/backend/nodes/equalfuncs.c @@ -83,6 +83,10 @@ #define COMPARE_LOCATION_FIELD(fldname) \ ((void) 0) +/* Compare a CoercionForm field (also a no-op, per comment in primnodes.h) */ +#define COMPARE_COERCIONFORM_FIELD(fldname) \ + ((void) 0) + /* * Stuff from primnodes.h @@ -235,16 +239,7 @@ _equalFuncExpr(const FuncExpr *a, const FuncExpr *b) COMPARE_SCALAR_FIELD(funcid); COMPARE_SCALAR_FIELD(funcresulttype); COMPARE_SCALAR_FIELD(funcretset); - - /* - * Special-case COERCE_DONTCARE, so that planner can build coercion nodes - * that are equal() to both explicit and implicit coercions. - */ - if (a->funcformat != b->funcformat && - a->funcformat != COERCE_DONTCARE && - b->funcformat != COERCE_DONTCARE) - return false; - + COMPARE_COERCIONFORM_FIELD(funcformat); COMPARE_SCALAR_FIELD(funccollid); COMPARE_SCALAR_FIELD(inputcollid); COMPARE_NODE_FIELD(args); @@ -448,16 +443,7 @@ _equalRelabelType(const RelabelType *a, const RelabelType *b) COMPARE_SCALAR_FIELD(resulttype); COMPARE_SCALAR_FIELD(resulttypmod); COMPARE_SCALAR_FIELD(resultcollid); - - /* - * Special-case COERCE_DONTCARE, so that planner can build coercion nodes - * that are equal() to both explicit and implicit coercions. - */ - if (a->relabelformat != b->relabelformat && - a->relabelformat != COERCE_DONTCARE && - b->relabelformat != COERCE_DONTCARE) - return false; - + COMPARE_COERCIONFORM_FIELD(relabelformat); COMPARE_LOCATION_FIELD(location); return true; @@ -469,16 +455,7 @@ _equalCoerceViaIO(const CoerceViaIO *a, const CoerceViaIO *b) COMPARE_NODE_FIELD(arg); COMPARE_SCALAR_FIELD(resulttype); COMPARE_SCALAR_FIELD(resultcollid); - - /* - * Special-case COERCE_DONTCARE, so that planner can build coercion nodes - * that are equal() to both explicit and implicit coercions. - */ - if (a->coerceformat != b->coerceformat && - a->coerceformat != COERCE_DONTCARE && - b->coerceformat != COERCE_DONTCARE) - return false; - + COMPARE_COERCIONFORM_FIELD(coerceformat); COMPARE_LOCATION_FIELD(location); return true; @@ -493,16 +470,7 @@ _equalArrayCoerceExpr(const ArrayCoerceExpr *a, const ArrayCoerceExpr *b) COMPARE_SCALAR_FIELD(resulttypmod); COMPARE_SCALAR_FIELD(resultcollid); COMPARE_SCALAR_FIELD(isExplicit); - - /* - * Special-case COERCE_DONTCARE, so that planner can build coercion nodes - * that are equal() to both explicit and implicit coercions. - */ - if (a->coerceformat != b->coerceformat && - a->coerceformat != COERCE_DONTCARE && - b->coerceformat != COERCE_DONTCARE) - return false; - + COMPARE_COERCIONFORM_FIELD(coerceformat); COMPARE_LOCATION_FIELD(location); return true; @@ -513,16 +481,7 @@ _equalConvertRowtypeExpr(const ConvertRowtypeExpr *a, const ConvertRowtypeExpr * { COMPARE_NODE_FIELD(arg); COMPARE_SCALAR_FIELD(resulttype); - - /* - * Special-case COERCE_DONTCARE, so that planner can build coercion nodes - * that are equal() to both explicit and implicit coercions. - */ - if (a->convertformat != b->convertformat && - a->convertformat != COERCE_DONTCARE && - b->convertformat != COERCE_DONTCARE) - return false; - + COMPARE_COERCIONFORM_FIELD(convertformat); COMPARE_LOCATION_FIELD(location); return true; @@ -589,16 +548,7 @@ _equalRowExpr(const RowExpr *a, const RowExpr *b) { COMPARE_NODE_FIELD(args); COMPARE_SCALAR_FIELD(row_typeid); - - /* - * Special-case COERCE_DONTCARE, so that planner can build coercion nodes - * that are equal() to both explicit and implicit coercions. - */ - if (a->row_format != b->row_format && - a->row_format != COERCE_DONTCARE && - b->row_format != COERCE_DONTCARE) - return false; - + COMPARE_COERCIONFORM_FIELD(row_format); COMPARE_NODE_FIELD(colnames); COMPARE_LOCATION_FIELD(location); @@ -684,16 +634,7 @@ _equalCoerceToDomain(const CoerceToDomain *a, const CoerceToDomain *b) COMPARE_SCALAR_FIELD(resulttype); COMPARE_SCALAR_FIELD(resulttypmod); COMPARE_SCALAR_FIELD(resultcollid); - - /* - * Special-case COERCE_DONTCARE, so that planner can build coercion nodes - * that are equal() to both explicit and implicit coercions. - */ - if (a->coercionformat != b->coercionformat && - a->coercionformat != COERCE_DONTCARE && - b->coercionformat != COERCE_DONTCARE) - return false; - + COMPARE_COERCIONFORM_FIELD(coercionformat); COMPARE_LOCATION_FIELD(location); return true; diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index fa6817c914..5894dd39c1 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -98,7 +98,6 @@ static bool contain_leaky_functions_walker(Node *node, void *context); static Relids find_nonnullable_rels_walker(Node *node, bool top_level); static List *find_nonnullable_vars_walker(Node *node, bool top_level); static bool is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK); -static bool set_coercionform_dontcare_walker(Node *node, void *context); static Node *eval_const_expressions_mutator(Node *node, eval_const_expressions_context *context); static List *simplify_or_arguments(List *args, @@ -2114,47 +2113,6 @@ strip_implicit_coercions(Node *node) return node; } -/* - * set_coercionform_dontcare: set all CoercionForm fields to COERCE_DONTCARE - * - * This is used to make index expressions and index predicates more easily - * comparable to clauses of queries. CoercionForm is not semantically - * significant (for cases where it does matter, the significant info is - * coded into the coercion function arguments) so we can ignore it during - * comparisons. Thus, for example, an index on "foo::int4" can match an - * implicit coercion to int4. - * - * Caution: the passed expression tree is modified in-place. - */ -void -set_coercionform_dontcare(Node *node) -{ - (void) set_coercionform_dontcare_walker(node, NULL); -} - -static bool -set_coercionform_dontcare_walker(Node *node, void *context) -{ - if (node == NULL) - return false; - if (IsA(node, FuncExpr)) - ((FuncExpr *) node)->funcformat = COERCE_DONTCARE; - else if (IsA(node, RelabelType)) - ((RelabelType *) node)->relabelformat = COERCE_DONTCARE; - else if (IsA(node, CoerceViaIO)) - ((CoerceViaIO *) node)->coerceformat = COERCE_DONTCARE; - else if (IsA(node, ArrayCoerceExpr)) - ((ArrayCoerceExpr *) node)->coerceformat = COERCE_DONTCARE; - else if (IsA(node, ConvertRowtypeExpr)) - ((ConvertRowtypeExpr *) node)->convertformat = COERCE_DONTCARE; - else if (IsA(node, RowExpr)) - ((RowExpr *) node)->row_format = COERCE_DONTCARE; - else if (IsA(node, CoerceToDomain)) - ((CoerceToDomain *) node)->coercionformat = COERCE_DONTCARE; - return expression_tree_walker(node, set_coercionform_dontcare_walker, - context); -} - /* * Helper for eval_const_expressions: check that datatype of an attribute * is still what it was when the expression was parsed. This is needed to diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c index 25f8785b63..abcd0ee574 100644 --- a/src/backend/optimizer/util/plancat.c +++ b/src/backend/optimizer/util/plancat.c @@ -665,12 +665,6 @@ get_relation_constraints(PlannerInfo *root, cexpr = (Node *) canonicalize_qual((Expr *) cexpr); - /* - * Also mark any coercion format fields as "don't care", so that - * we can match to both explicit and implicit coercions. - */ - set_coercionform_dontcare(cexpr); - /* Fix Vars to have the desired varno */ if (varno != 1) ChangeVarNodes(cexpr, 1, varno, 0); diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c index 0cdd30d15b..8c9ebe0f6f 100644 --- a/src/backend/utils/cache/relcache.c +++ b/src/backend/utils/cache/relcache.c @@ -3549,12 +3549,6 @@ RelationGetIndexExpressions(Relation relation) */ result = (List *) eval_const_expressions(NULL, (Node *) result); - /* - * Also mark any coercion format fields as "don't care", so that the - * planner can match to both explicit and implicit coercions. - */ - set_coercionform_dontcare((Node *) result); - /* May as well fix opfuncids too */ fix_opfuncids((Node *) result); @@ -3621,12 +3615,6 @@ RelationGetIndexPredicate(Relation relation) result = (List *) canonicalize_qual((Expr *) result); - /* - * Also mark any coercion format fields as "don't care", so that the - * planner can match to both explicit and implicit coercions. - */ - set_coercionform_dontcare((Node *) result); - /* Also convert to implicit-AND format */ result = make_ands_implicit((Expr *) result); diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index cd4561dcf4..daabcb6cf9 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -317,6 +317,12 @@ typedef enum CoercionContext /* * CoercionForm - information showing how to display a function-call node + * + * NB: equal() ignores CoercionForm fields, therefore this *must* not carry + * any semantically significant information. We need that behavior so that + * the planner will consider equivalent implicit and explicit casts to be + * equivalent. In cases where those actually behave differently, the coercion + * function's arguments will be different. */ typedef enum CoercionForm { diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h index ac75bd4d6e..acff7ba1b7 100644 --- a/src/include/optimizer/clauses.h +++ b/src/include/optimizer/clauses.h @@ -79,8 +79,6 @@ extern void CommuteRowCompareExpr(RowCompareExpr *clause); extern Node *strip_implicit_coercions(Node *node); -extern void set_coercionform_dontcare(Node *node); - extern Node *eval_const_expressions(PlannerInfo *root, Node *node); extern Node *estimate_expression_value(PlannerInfo *root, Node *node);