diff options
Diffstat (limited to 'src/backend/optimizer/path/joinrels.c')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 36 |
1 files changed, 15 insertions, 21 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 1287037c0ba..8df5c21f1fd 100644 --- a/src/backend/optimizer/path/joinrels.c +++ b/src/backend/optimizer/path/joinrels.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.90 2008/01/01 19:45:50 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.91 2008/01/11 04:02:18 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -838,33 +838,27 @@ has_join_restriction(PlannerInfo *root, RelOptInfo *rel) * Detect whether the specified relation can legally be joined * to any other rels using join clauses. * - * We consider only joins to single other relations. This is sufficient - * to get a "true" result in most real queries, and an occasional erroneous - * "false" will only cost a bit more planning time. The reason for this - * limitation is that considering joins to other joins would require proving - * that the other join rel can legally be formed, which seems like too much - * trouble for something that's only a heuristic to save planning time. + * We consider only joins to single other relations in the current + * initial_rels list. This is sufficient to get a "true" result in most real + * queries, and an occasional erroneous "false" will only cost a bit more + * planning time. The reason for this limitation is that considering joins to + * other joins would require proving that the other join rel can legally be + * formed, which seems like too much trouble for something that's only a + * heuristic to save planning time. (Note: we must look at initial_rels + * and not all of the query, since when we are planning a sub-joinlist we + * may be forced to make clauseless joins within initial_rels even though + * there are join clauses linking to other parts of the query.) */ static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel) { - Index rti; + ListCell *lc; - for (rti = 1; rti < root->simple_rel_array_size; rti++) + foreach(lc, root->initial_rels) { - RelOptInfo *rel2 = root->simple_rel_array[rti]; + RelOptInfo *rel2 = (RelOptInfo *) lfirst(lc); - /* there may be empty slots corresponding to non-baserel RTEs */ - if (rel2 == NULL) - continue; - - Assert(rel2->relid == rti); /* sanity check on array */ - - /* ignore RTEs that are "other rels" */ - if (rel2->reloptkind != RELOPT_BASEREL) - continue; - - /* ignore RTEs that are already in "rel" */ + /* ignore rels that are already in "rel" */ if (bms_overlap(rel->relids, rel2->relids)) continue; |