diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 40 |
1 files changed, 37 insertions, 3 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 25bd55dadf3..124534914f8 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -8,13 +8,14 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.134 2005/06/10 03:32:21 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.135 2005/07/23 21:05:46 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" +#include "nodes/makefuncs.h" #ifdef OPTIMIZER_DEBUG #include "nodes/print.h" #endif @@ -25,6 +26,7 @@ #include "optimizer/paths.h" #include "optimizer/plancat.h" #include "optimizer/planner.h" +#include "optimizer/predtest.h" #include "optimizer/prep.h" #include "optimizer/var.h" #include "parser/parsetree.h" @@ -34,6 +36,7 @@ /* These parameters are set by GUC */ +bool enable_constraint_exclusion = false; bool enable_geqo = false; /* just in case GUC doesn't set it */ int geqo_threshold; @@ -311,7 +314,37 @@ set_inherited_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, childOID); /* - * Now compute child access paths, and save the cheapest. + * If we can prove we don't need to scan this child via constraint + * exclusion, just ignore it. (We have to have converted the + * baserestrictinfo Vars before we can make the test.) + */ + if (enable_constraint_exclusion) + { + List *constraint_pred; + + constraint_pred = get_relation_constraints(childOID, childrel); + /* + * 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)) + { + /* + * 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, + childrel->baserestrictinfo)) + continue; + } + } + + /* + * Compute the child's access paths, and save the cheapest. */ set_plain_rel_pathlist(root, childrel, childrte); @@ -345,7 +378,8 @@ set_inherited_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, /* * Finally, build Append path and install it as the only access path - * for the parent rel. + * for the parent rel. (Note: this is correct even if we have zero + * or one live subpath due to constraint exclusion.) */ add_path(rel, (Path *) create_append_path(rel, subpaths)); |