diff options
Diffstat (limited to 'src/backend/optimizer/path/joinrels.c')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 94 |
1 files changed, 51 insertions, 43 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 2492f17ea9b..929a977112d 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 1.51 2001/02/16 00:03:07 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinrels.c,v 1.52 2001/03/22 03:59:35 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -19,7 +19,7 @@ static RelOptInfo *make_join_rel(Query *root, RelOptInfo *rel1, - RelOptInfo *rel2, JoinType jointype); + RelOptInfo *rel2, JoinType jointype); /* @@ -44,18 +44,19 @@ make_rels_by_joins(Query *root, int level, List **joinrels) /* * First, consider left-sided and right-sided plans, in which rels of - * exactly level-1 member relations are joined against initial 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 initial rels not already contained in it. + * exactly level-1 member relations are joined against initial + * 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 initial rels not already + * contained in it. * - * In the first pass (level == 2), we try to join each initial rel to each - * initial rel that appears later in joinrels[1]. (The mirror-image - * joins are handled automatically by make_join_rel.) In later - * passes, we try to join rels of size level-1 from joinrels[level-1] - * to each initial rel in joinrels[1]. + * In the first pass (level == 2), we try to join each initial rel to + * each initial rel that appears later in joinrels[1]. (The + * mirror-image joins are handled automatically by make_join_rel.) In + * later passes, we try to join rels of size level-1 from + * joinrels[level-1] to each initial rel in joinrels[1]. */ - foreach(r, joinrels[level-1]) + foreach(r, joinrels[level - 1]) { RelOptInfo *old_rel = (RelOptInfo *) lfirst(r); List *other_rels; @@ -73,9 +74,9 @@ make_rels_by_joins(Query *root, int level, List **joinrels) * 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 where we - * have those other rels collected into a join rel. See also - * the last-ditch case below. + * "bushy plan" join code in a higher-level pass where we have + * those other rels collected into a join rel. See also the + * last-ditch case below. */ new_rels = make_rels_by_clause_joins(root, old_rel, @@ -94,16 +95,16 @@ make_rels_by_joins(Query *root, int level, List **joinrels) } /* - * At levels above 2 we will generate the same joined relation - * in multiple ways --- for example (a join b) join c is the same + * At levels above 2 we will generate the same joined relation in + * multiple ways --- for example (a join b) join c is the same * RelOptInfo as (b join c) join a, though the second case will - * add a different set of Paths to it. To avoid making extra work - * for subsequent passes, do not enter the same RelOptInfo into our - * output list multiple times. + * add a different set of Paths to it. To avoid making extra work + * for subsequent passes, do not enter the same RelOptInfo into + * our output list multiple times. */ foreach(nr, new_rels) { - RelOptInfo *jrel = (RelOptInfo *) lfirst(nr); + RelOptInfo *jrel = (RelOptInfo *) lfirst(nr); if (!ptrMember(jrel, result_rels)) result_rels = lcons(jrel, result_rels); @@ -111,20 +112,21 @@ make_rels_by_joins(Query *root, int level, List **joinrels) } /* - * Now, consider "bushy plans" in which relations of k initial rels are - * joined to relations of level-k initial rels, for 2 <= k <= level-2. + * Now, consider "bushy plans" in which relations of k initial rels + * are joined to relations of level-k initial rels, for 2 <= k <= + * 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 * planning time. */ - for (k = 2; ; k++) + for (k = 2;; k++) { int other_level = level - k; /* - * Since make_join_rel(x, y) handles both x,y and y,x cases, - * we only need to go as far as the halfway point. + * Since make_join_rel(x, y) handles both x,y and y,x cases, we + * only need to go as far as the halfway point. */ if (k > other_level) break; @@ -139,7 +141,7 @@ make_rels_by_joins(Query *root, int level, List **joinrels) continue; /* we ignore clauseless joins here */ if (k == other_level) - other_rels = lnext(r); /* only consider remaining rels */ + other_rels = lnext(r); /* only consider remaining rels */ else other_rels = joinrels[other_level]; @@ -153,8 +155,8 @@ make_rels_by_joins(Query *root, int level, List **joinrels) /* * 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. + * pair of rels. Do so if there is at least one + * usable join clause. */ foreach(i, old_rel->joininfo) { @@ -170,7 +172,8 @@ make_rels_by_joins(Query *root, int level, List **joinrels) /* Avoid making duplicate entries ... */ if (!ptrMember(jrel, result_rels)) result_rels = lcons(jrel, result_rels); - break; /* need not consider more joininfos */ + break; /* need not consider more + * joininfos */ } } } @@ -180,31 +183,34 @@ make_rels_by_joins(Query *root, int level, List **joinrels) /* * Last-ditch effort: if we failed to find any usable joins so far, - * force a set of cartesian-product joins to be generated. This + * force a set of cartesian-product joins to be generated. This * handles the special case where all the available rels have join - * clauses but we cannot use any of the joins yet. An example is + * clauses but we cannot use any of the joins yet. An example is * * SELECT * FROM a,b,c WHERE (a.f1 + b.f2 + c.f3) = 0; * - * The join clause will be usable at level 3, but at level 2 we have - * no choice but to make cartesian joins. We consider only left-sided + * The join clause will be usable at level 3, but at level 2 we have no + * choice but to make cartesian joins. We consider only left-sided * and right-sided cartesian joins in this case (no bushy). */ if (result_rels == NIL) { - /* This loop is just like the first one, except we always call + + /* + * This loop is just like the first one, except we always call * make_rels_by_clauseless_joins(). */ - foreach(r, joinrels[level-1]) + foreach(r, joinrels[level - 1]) { RelOptInfo *old_rel = (RelOptInfo *) lfirst(r); List *other_rels; if (level == 2) - other_rels = lnext(r); /* only consider remaining initial - * rels */ + other_rels = lnext(r); /* only consider remaining initial + * rels */ else - other_rels = joinrels[1]; /* consider all initial rels */ + other_rels = joinrels[1]; /* consider all initial + * rels */ new_rels = make_rels_by_clauseless_joins(root, old_rel, @@ -212,7 +218,7 @@ make_rels_by_joins(Query *root, int level, List **joinrels) foreach(nr, new_rels) { - RelOptInfo *jrel = (RelOptInfo *) lfirst(nr); + RelOptInfo *jrel = (RelOptInfo *) lfirst(nr); if (!ptrMember(jrel, result_rels)) result_rels = lcons(jrel, result_rels); @@ -266,6 +272,7 @@ make_rels_by_clause_joins(Query *root, RelOptInfo *jrel; jrel = make_join_rel(root, old_rel, other_rel, JOIN_INNER); + /* * Avoid entering same joinrel into our output list more * than once. (make_rels_by_joins doesn't really care, @@ -310,9 +317,10 @@ make_rels_by_clauseless_joins(Query *root, RelOptInfo *jrel; jrel = make_join_rel(root, old_rel, other_rel, JOIN_INNER); + /* - * As long as given other_rels are distinct, don't need - * to test to see if jrel is already part of output list. + * As long as given other_rels are distinct, don't need to + * test to see if jrel is already part of output list. */ result = lcons(jrel, result); } @@ -325,7 +333,7 @@ make_rels_by_clauseless_joins(Query *root, /* * make_jointree_rel * Find or build a RelOptInfojoin rel representing a specific - * jointree item. For JoinExprs, we only consider the construction + * jointree item. For JoinExprs, we only consider the construction * path that corresponds exactly to what the user wrote. */ RelOptInfo * |