diff options
Diffstat (limited to 'src/backend/optimizer/path/joinpath.c')
| -rw-r--r-- | src/backend/optimizer/path/joinpath.c | 50 |
1 files changed, 38 insertions, 12 deletions
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c index 6069a34d879..65d0d8fa358 100644 --- a/src/backend/optimizer/path/joinpath.c +++ b/src/backend/optimizer/path/joinpath.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.73 2002/11/30 00:08:16 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.74 2002/11/30 05:21:02 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -281,8 +281,9 @@ sort_inner_and_outer(Query *root, * only outer paths that are already ordered well enough for merging). * * We always generate a nestloop path for each available outer path. - * In fact we may generate as many as three: one on the cheapest-total-cost - * inner path, one on the cheapest-startup-cost inner path (if different), + * In fact we may generate as many as four: one on the cheapest-total-cost + * inner path, one on the same with materialization, one on the + * cheapest-startup-cost inner path (if different), * and one on the best inner-indexscan path (if any). * * We also consider mergejoins if mergejoin clauses are available. We have @@ -315,7 +316,8 @@ match_unsorted_outer(Query *root, { bool nestjoinOK; bool useallclauses; - Path *bestinnerjoin; + Path *matpath = NULL; + Path *bestinnerjoin = NULL; List *i; /* @@ -345,12 +347,26 @@ match_unsorted_outer(Query *root, break; } - /* - * Get the best innerjoin indexpath (if any) for this outer rel. It's - * the same for all outer paths. - */ - bestinnerjoin = best_inner_indexscan(root, innerrel, - outerrel->relids, jointype); + if (nestjoinOK) + { + /* + * If the cheapest inner path is a join or seqscan, we should consider + * materializing it. (This is a heuristic: we could consider it + * always, but for inner indexscans it's probably a waste of time.) + */ + if (!(IsA(innerrel->cheapest_total_path, IndexPath) || + IsA(innerrel->cheapest_total_path, TidPath))) + matpath = (Path *) + create_material_path(innerrel, + innerrel->cheapest_total_path); + + /* + * Get the best innerjoin indexpath (if any) for this outer rel. It's + * the same for all outer paths. + */ + bestinnerjoin = best_inner_indexscan(root, innerrel, + outerrel->relids, jointype); + } foreach(i, outerrel->pathlist) { @@ -376,8 +392,9 @@ match_unsorted_outer(Query *root, { /* * Always consider a nestloop join with this outer and - * cheapest-total-cost inner. Consider nestloops using the - * cheapest-startup-cost inner as well, and the best innerjoin + * cheapest-total-cost inner. When appropriate, also consider + * using the materialized form of the cheapest inner, the + * cheapest-startup-cost inner path, and the best innerjoin * indexpath. */ add_path(joinrel, (Path *) @@ -388,6 +405,15 @@ match_unsorted_outer(Query *root, innerrel->cheapest_total_path, restrictlist, merge_pathkeys)); + if (matpath != NULL) + add_path(joinrel, (Path *) + create_nestloop_path(root, + joinrel, + jointype, + outerpath, + matpath, + restrictlist, + merge_pathkeys)); if (innerrel->cheapest_startup_path != innerrel->cheapest_total_path) add_path(joinrel, (Path *) |