diff options
Diffstat (limited to 'src/backend/optimizer/path/joinrels.c')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 36 |
1 files changed, 20 insertions, 16 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 540ec0ada5a..5d25e0d28b8 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 1.70 2004/08/29 04:12:33 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.71 2004/08/29 05:06:43 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -70,7 +70,8 @@ make_rels_by_joins(Query *root, int level, List **joinrels) other_rels = lnext(r); /* only consider remaining initial * rels */ else - other_rels = list_head(joinrels[1]); /* consider all initial rels */ + other_rels = list_head(joinrels[1]); /* consider all initial + * rels */ if (old_rel->joininfo != NIL) { @@ -84,12 +85,14 @@ make_rels_by_joins(Query *root, int level, List **joinrels) new_rels = make_rels_by_clause_joins(root, old_rel, other_rels); + /* - * An exception occurs when there is a clauseless join inside an - * IN (sub-SELECT) construct. Here, the members of the subselect - * all have join clauses (against the stuff outside the IN), but - * they *must* be joined to each other before we can make use of - * those join clauses. So do the clauseless join bit. + * An exception occurs when there is a clauseless join inside + * an IN (sub-SELECT) construct. Here, the members of the + * subselect all have join clauses (against the stuff outside + * the IN), but they *must* be joined to each other before we + * can make use of those join clauses. So do the clauseless + * join bit. * * See also the last-ditch case below. */ @@ -223,8 +226,8 @@ make_rels_by_joins(Query *root, int level, List **joinrels) other_rels = lnext(r); /* only consider remaining initial * rels */ else - other_rels = list_head(joinrels[1]); /* consider all initial - * rels */ + other_rels = list_head(joinrels[1]); /* consider all initial + * rels */ new_rels = make_rels_by_clauseless_joins(root, old_rel, @@ -241,11 +244,11 @@ make_rels_by_joins(Query *root, int level, List **joinrels) /*---------- * When IN clauses are involved, there may be no legal way to make - * an N-way join for some values of N. For example consider + * an N-way join for some values of N. For example consider * * SELECT ... FROM t1 WHERE - * x IN (SELECT ... FROM t2,t3 WHERE ...) AND - * y IN (SELECT ... FROM t4,t5 WHERE ...) + * x IN (SELECT ... FROM t2,t3 WHERE ...) AND + * y IN (SELECT ... FROM t4,t5 WHERE ...) * * We will flatten this query to a 5-way join problem, but there are * no 4-way joins that make_join_rel() will consider legal. We have @@ -486,8 +489,8 @@ make_join_rel(Query *root, RelOptInfo *rel1, RelOptInfo *rel2, /* * This IN clause is not relevant unless its RHS overlaps the - * proposed join. (Check this first as a fast path for dismissing - * most irrelevant INs quickly.) + * proposed join. (Check this first as a fast path for + * dismissing most irrelevant INs quickly.) */ if (!bms_overlap(ininfo->righthand, joinrelids)) continue; @@ -516,8 +519,9 @@ make_join_rel(Query *root, RelOptInfo *rel1, RelOptInfo *rel2, * some other rel(s). * * If we already joined IN's RHS to any other rels in either - * input path, then this join is not constrained (the necessary - * work was done at the lower level where that join occurred). + * input path, then this join is not constrained (the + * necessary work was done at the lower level where that join + * occurred). */ if (bms_is_subset(ininfo->righthand, rel1->relids) && !bms_equal(ininfo->righthand, rel1->relids)) |