diff options
Diffstat (limited to 'src/backend/optimizer/util')
| -rw-r--r-- | src/backend/optimizer/util/plancat.c | 52 |
1 files changed, 50 insertions, 2 deletions
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c index c926ae5d488..b6dcfa144f2 100644 --- a/src/backend/optimizer/util/plancat.c +++ b/src/backend/optimizer/util/plancat.c @@ -9,7 +9,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.117 2006/01/31 21:39:24 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.118 2006/02/04 23:03:20 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -25,6 +25,7 @@ #include "nodes/makefuncs.h" #include "optimizer/clauses.h" #include "optimizer/plancat.h" +#include "optimizer/predtest.h" #include "optimizer/prep.h" #include "optimizer/tlist.h" #include "parser/parsetree.h" @@ -40,8 +41,13 @@ #include "miscadmin.h" +/* GUC parameter */ +bool constraint_exclusion = false; + + static void estimate_rel_size(Relation rel, int32 *attr_widths, BlockNumber *pages, double *tuples); +static List *get_relation_constraints(Oid relationObjectId, RelOptInfo *rel); /* @@ -360,7 +366,7 @@ estimate_rel_size(Relation rel, int32 *attr_widths, * run, and in many cases it won't be invoked at all, so there seems no * point in caching the data in RelOptInfo. */ -List * +static List * get_relation_constraints(Oid relationObjectId, RelOptInfo *rel) { List *result = NIL; @@ -425,6 +431,48 @@ get_relation_constraints(Oid relationObjectId, RelOptInfo *rel) /* + * relation_excluded_by_constraints + * + * Detect whether the relation need not be scanned because it has CHECK + * constraints that conflict with the query's WHERE clause. + */ +bool +relation_excluded_by_constraints(RelOptInfo *rel, RangeTblEntry *rte) +{ + List *constraint_pred; + + /* Skip the test if constraint exclusion is disabled */ + if (!constraint_exclusion) + return false; + + /* Only plain relations have constraints */ + if (rte->rtekind != RTE_RELATION || rte->inh) + return false; + + /* OK to fetch the constraint expressions */ + constraint_pred = get_relation_constraints(rte->relid, rel); + + /* + * We do not currently enforce that CHECK constraints contain only + * immutable functions, so it's necessary to check here. We daren't draw + * conclusions from plan-time evaluation of non-immutable functions. + */ + if (contain_mutable_functions((Node *) constraint_pred)) + return false; + + /* + * The constraints are effectively ANDed together, so we can just try to + * refute the entire collection at once. This may allow us to make proofs + * that would fail if we took them individually. + */ + if (predicate_refuted_by(constraint_pred, rel->baserestrictinfo)) + return true; + + return false; +} + + +/* * build_physical_tlist * * Build a targetlist consisting of exactly the relation's user attributes, |