diff options
Diffstat (limited to 'src/backend/optimizer/plan/createplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/createplan.c | 78 |
1 files changed, 73 insertions, 5 deletions
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c index eb7e922d9a1..d78dd2c1e83 100644 --- a/src/backend/optimizer/plan/createplan.c +++ b/src/backend/optimizer/plan/createplan.c @@ -10,7 +10,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.133 2003/01/22 00:07:00 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.134 2003/02/03 15:07:07 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -34,6 +34,7 @@ static Scan *create_scan_plan(Query *root, Path *best_path); +static bool use_physical_tlist(RelOptInfo *rel); static Join *create_join_plan(Query *root, JoinPath *best_path); static Append *create_append_plan(Query *root, AppendPath *best_path); static Result *create_result_plan(Query *root, ResultPath *best_path); @@ -185,15 +186,41 @@ create_plan(Query *root, Path *best_path) static Scan * create_scan_plan(Query *root, Path *best_path) { - Scan *plan; - List *tlist = best_path->parent->targetlist; + RelOptInfo *rel = best_path->parent; + List *tlist; List *scan_clauses; + Scan *plan; + + /* + * For table scans, rather than using the relation targetlist (which is + * only those Vars actually needed by the query), we prefer to generate a + * tlist containing all Vars in order. This will allow the executor to + * optimize away projection of the table tuples, if possible. (Note that + * planner.c may replace the tlist we generate here, forcing projection to + * occur.) + */ + if (use_physical_tlist(rel)) + { + int resdomno = 1; + List *v; + + tlist = NIL; + foreach(v, rel->varlist) + { + Var *var = (Var *) lfirst(v); + + tlist = lappend(tlist, create_tl_element(var, resdomno)); + resdomno++; + } + } + else + tlist = rel->targetlist; /* * Extract the relevant restriction clauses from the parent relation; * the executor must apply all these restrictions during the scan. */ - scan_clauses = get_actual_clauses(best_path->parent->baserestrictinfo); + scan_clauses = get_actual_clauses(rel->baserestrictinfo); /* Sort clauses into best execution order */ scan_clauses = order_qual_clauses(root, scan_clauses); @@ -242,6 +269,47 @@ create_scan_plan(Query *root, Path *best_path) } /* + * use_physical_tlist + * Decide whether to use a tlist matching relation structure, + * rather than only those Vars actually referenced. + */ +static bool +use_physical_tlist(RelOptInfo *rel) +{ + List *t; + + /* + * Currently, can't do this for subquery or function scans. (This + * is mainly because we don't set up the necessary info when creating + * their RelOptInfo nodes.) + */ + if (rel->rtekind != RTE_RELATION) + return false; + /* + * Can't do it with inheritance cases either (mainly because Append + * doesn't project). + */ + if (rel->reloptkind != RELOPT_BASEREL) + return false; + /* + * Can't do it if any system columns are requested, either. (This could + * possibly be fixed but would take some fragile assumptions in setrefs.c, + * I think.) + */ + foreach(t, rel->targetlist) + { + TargetEntry *tle = (TargetEntry *) lfirst(t); + Var *var = (Var *) tle->expr; + + if (!var || !IsA(var, Var)) + return false; /* probably can't happen */ + if (var->varattno <= 0) + return false; /* system column! */ + } + return true; +} + +/* * create_join_plan * Create a join plan for 'best_path' and (recursively) plans for its * inner and outer paths. @@ -399,7 +467,7 @@ create_material_plan(Query *root, MaterialPath *best_path) subplan = create_plan(root, best_path->subpath); - plan = make_material(best_path->path.parent->targetlist, subplan); + plan = make_material(subplan->targetlist, subplan); copy_path_costsize(&plan->plan, (Path *) best_path); |