diff options
Diffstat (limited to 'src/backend/optimizer/path/joinrels.c')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 60 |
1 files changed, 34 insertions, 26 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index e872b67623..09003eb9fa 100644 --- a/src/backend/optimizer/path/joinrels.c +++ b/src/backend/optimizer/path/joinrels.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinrels.c,v 1.43 2000/02/07 04:40:59 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinrels.c,v 1.44 2000/04/12 17:15:20 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -22,7 +22,7 @@ static RelOptInfo *make_join_rel(Query *root, RelOptInfo *rel1, - RelOptInfo *rel2); + RelOptInfo *rel2); /* @@ -44,22 +44,23 @@ make_rels_by_joins(Query *root, int level) /* * First, consider left-sided and right-sided plans, in which rels of * exactly level-1 member relations are joined against base relations. - * We prefer to join using join clauses, but if we find a rel of level-1 - * members that has no join clauses, we will generate Cartesian-product - * joins against all base rels not already contained in it. + * We prefer to join using join clauses, but if we find a rel of + * level-1 members that has no join clauses, we will generate + * Cartesian-product joins against all base rels not already contained + * in it. * * In the first pass (level == 2), we try to join each base rel to each * base rel that appears later in base_rel_list. (The mirror-image - * joins are handled automatically by make_join_rel.) In later passes, - * we try to join rels of size level-1 from join_rel_list to each - * base rel in base_rel_list. + * joins are handled automatically by make_join_rel.) In later + * passes, we try to join rels of size level-1 from join_rel_list to + * each base rel in base_rel_list. * * We assume that the rels already present in join_rel_list appear in * decreasing order of level (number of members). This should be true * since we always add new higher-level rels to the front of the list. */ if (level == 2) - r = root->base_rel_list; /* level-1 is base rels */ + r = root->base_rel_list;/* level-1 is base rels */ else r = root->join_rel_list; for (; r != NIL; r = lnext(r)) @@ -68,21 +69,23 @@ make_rels_by_joins(Query *root, int level) int old_level = length(old_rel->relids); List *other_rels; - if (old_level != level-1) + if (old_level != level - 1) break; if (level == 2) - other_rels = lnext(r); /* only consider remaining base rels */ + other_rels = lnext(r); /* only consider remaining base + * rels */ else - other_rels = root->base_rel_list; /* consider all base rels */ + other_rels = root->base_rel_list; /* consider all base rels */ if (old_rel->joininfo != NIL) { + /* - * Note that if all available join clauses for this rel require - * more than one other rel, we will fail to make any joins against - * it here. That's OK; it'll be considered by "bushy plan" join - * code in a higher-level pass. + * Note that if all available join clauses for this rel + * require more than one other rel, we will fail to make any + * joins against it here. That's OK; it'll be considered by + * "bushy plan" join code in a higher-level pass. */ make_rels_by_clause_joins(root, old_rel, @@ -90,6 +93,7 @@ make_rels_by_joins(Query *root, int level) } else { + /* * Oops, we have a relation that is not joined to any other * relation. Cartesian product time. @@ -103,10 +107,11 @@ make_rels_by_joins(Query *root, int level) /* * Now, consider "bushy plans" in which relations of k base rels are * joined to relations of level-k base rels, for 2 <= k <= level-2. - * The previous loop left r pointing to the first rel of level level-2. + * The previous loop left r pointing to the first rel of level + * level-2. * - * We only consider bushy-plan joins for pairs of rels where there is - * a suitable join clause, in order to avoid unreasonable growth of + * We only consider bushy-plan joins for pairs of rels where there is a + * suitable join clause, in order to avoid unreasonable growth of * planning time. */ for (; r != NIL; r = lnext(r)) @@ -115,8 +120,9 @@ make_rels_by_joins(Query *root, int level) int old_level = length(old_rel->relids); List *r2; - /* We can quit once past the halfway point (make_join_rel took care - * of making the opposite-direction joins) + /* + * We can quit once past the halfway point (make_join_rel took + * care of making the opposite-direction joins) */ if (old_level * 2 < level) break; @@ -137,8 +143,10 @@ make_rels_by_joins(Query *root, int level) { List *i; - /* OK, we can build a rel of the right level from this pair of - * rels. Do so if there is at least one usable join clause. + /* + * OK, we can build a rel of the right level from this + * pair of rels. Do so if there is at least one usable + * join clause. */ foreach(i, old_rel->joininfo) { @@ -192,7 +200,7 @@ make_rels_by_clause_joins(Query *root, foreach(j, other_rels) { - RelOptInfo *other_rel = (RelOptInfo *) lfirst(j); + RelOptInfo *other_rel = (RelOptInfo *) lfirst(j); if (is_subseti(unjoined_relids, other_rel->relids)) result = make_join_rel(root, old_rel, other_rel); @@ -251,8 +259,8 @@ make_rels_by_clauseless_joins(Query *root, static RelOptInfo * make_join_rel(Query *root, RelOptInfo *rel1, RelOptInfo *rel2) { - RelOptInfo *joinrel; - List *restrictlist; + RelOptInfo *joinrel; + List *restrictlist; /* * Find or build the join RelOptInfo, and compute the restrictlist |