diff options
Diffstat (limited to 'src/backend/optimizer/path/costsize.c')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 67 |
1 files changed, 20 insertions, 47 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index cb0b657acb..94202cda4b 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -49,7 +49,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.118 2003/12/18 03:46:45 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.119 2004/01/04 03:51:52 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1625,15 +1625,12 @@ cost_qual_eval_walker(Node *node, QualCost *total) * The input can be either an implicitly-ANDed list of boolean * expressions, or a list of RestrictInfo nodes (typically the latter). * - * The "quick" part comes from caching the selectivity estimates so we can - * avoid recomputing them later. (Since the same clauses are typically - * examined over and over in different possible join trees, this makes a - * big difference.) - * - * The "dirty" part comes from the fact that the selectivities of multiple - * clauses are estimated independently and multiplied together. Now + * This is quick-and-dirty because we bypass clauselist_selectivity, and + * simply multiply the independent clause selectivities together. Now * clauselist_selectivity often can't do any better than that anyhow, but - * for some situations (such as range constraints) it is smarter. + * for some situations (such as range constraints) it is smarter. However, + * we can't effectively cache the results of clauselist_selectivity, whereas + * the individual clause selectivities can be and are cached. * * Since we are only using the results to estimate how many potential * output tuples are generated and passed through qpqual checking, it @@ -1648,33 +1645,9 @@ approx_selectivity(Query *root, List *quals, JoinType jointype) foreach(l, quals) { Node *qual = (Node *) lfirst(l); - Selectivity selec; - /* - * RestrictInfo nodes contain a this_selec field reserved for this - * routine's use, so that it's not necessary to evaluate the qual - * clause's selectivity more than once. If the clause's - * selectivity hasn't been computed yet, the field will contain - * -1. - */ - if (qual && IsA(qual, RestrictInfo)) - { - RestrictInfo *restrictinfo = (RestrictInfo *) qual; - - if (restrictinfo->this_selec < 0) - restrictinfo->this_selec = - clause_selectivity(root, - (Node *) restrictinfo->clause, - 0, - jointype); - selec = restrictinfo->this_selec; - } - else - { - /* If it's a bare expression, must always do it the hard way */ - selec = clause_selectivity(root, qual, 0, jointype); - } - total *= selec; + /* Note that clause_selectivity will be able to cache its result */ + total *= clause_selectivity(root, qual, 0, jointype); } return total; } @@ -1702,10 +1675,10 @@ set_baserel_size_estimates(Query *root, RelOptInfo *rel) Assert(rel->relid > 0); temp = rel->tuples * - restrictlist_selectivity(root, - rel->baserestrictinfo, - rel->relid, - JOIN_INNER); + clauselist_selectivity(root, + rel->baserestrictinfo, + 0, + JOIN_INNER); /* * Force estimate to be at least one row, to make explain output look @@ -1765,10 +1738,10 @@ set_joinrel_size_estimates(Query *root, RelOptInfo *rel, * not double-counting them because they were not considered in * estimating the sizes of the component rels. */ - selec = restrictlist_selectivity(root, - restrictlist, - 0, - jointype); + selec = clauselist_selectivity(root, + restrictlist, + 0, + jointype); /* * Basically, we multiply size of Cartesian product by selectivity. @@ -1875,10 +1848,10 @@ set_function_size_estimates(Query *root, RelOptInfo *rel) /* Now estimate number of output rows */ temp = rel->tuples * - restrictlist_selectivity(root, - rel->baserestrictinfo, - rel->relid, - JOIN_INNER); + clauselist_selectivity(root, + rel->baserestrictinfo, + 0, + JOIN_INNER); /* * Force estimate to be at least one row, to make explain output look |