From b29f68f611e26377306a9ba2210a589b472c8544 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 16 Feb 2001 00:03:08 +0000 Subject: [PATCH] Take OUTER JOIN semantics into account when estimating the size of join relations. It's not very bright, but at least it now knows that A LEFT JOIN B must produce at least as many rows as are in A ... --- src/backend/optimizer/path/costsize.c | 35 +++++++++++++++++++++++++-- src/backend/optimizer/path/joinrels.c | 4 +-- src/backend/optimizer/util/relnode.c | 6 +++-- src/include/optimizer/cost.h | 3 ++- src/include/optimizer/pathnode.h | 10 +++++--- 5 files changed, 47 insertions(+), 11 deletions(-) diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index cc9e49b9e2..8e88e46d57 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -41,7 +41,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.67 2001/02/15 17:46:40 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.68 2001/02/16 00:03:07 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -837,11 +837,12 @@ void set_joinrel_size_estimates(Query *root, RelOptInfo *rel, RelOptInfo *outer_rel, RelOptInfo *inner_rel, + JoinType jointype, List *restrictlist) { double temp; - /* cartesian product */ + /* Start with the Cartesian product */ temp = outer_rel->rows * inner_rel->rows; /* @@ -854,6 +855,35 @@ set_joinrel_size_estimates(Query *root, RelOptInfo *rel, restrictlist, 0); + /* + * If we are doing an outer join, take that into account: the output + * must be at least as large as the non-nullable input. (Is there any + * chance of being even smarter?) + */ + switch (jointype) + { + case JOIN_INNER: + break; + case JOIN_LEFT: + if (temp < outer_rel->rows) + temp = outer_rel->rows; + break; + case JOIN_RIGHT: + if (temp < inner_rel->rows) + temp = inner_rel->rows; + break; + case JOIN_FULL: + if (temp < outer_rel->rows) + temp = outer_rel->rows; + if (temp < inner_rel->rows) + temp = inner_rel->rows; + break; + default: + elog(ERROR, "set_joinrel_size_estimates: unsupported join type %d", + (int) jointype); + break; + } + /* * Force estimate to be at least one row, to make explain output look * better and to avoid possible divide-by-zero when interpolating @@ -861,6 +891,7 @@ set_joinrel_size_estimates(Query *root, RelOptInfo *rel, */ if (temp < 1.0) temp = 1.0; + rel->rows = temp; /* diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 2a59ed43e4..2492f17ea9 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 1.50 2001/01/24 19:42:58 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinrels.c,v 1.51 2001/02/16 00:03:07 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -394,7 +394,7 @@ make_join_rel(Query *root, RelOptInfo *rel1, RelOptInfo *rel2, * Find or build the join RelOptInfo, and compute the restrictlist * that goes with this particular joining. */ - joinrel = get_join_rel(root, rel1, rel2, &restrictlist); + joinrel = get_join_rel(root, rel1, rel2, jointype, &restrictlist); /* * Consider paths using each rel as both outer and inner. diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c index 57827c813f..b4764ab6f8 100644 --- a/src/backend/optimizer/util/relnode.c +++ b/src/backend/optimizer/util/relnode.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/util/relnode.c,v 1.31 2001/01/24 19:43:00 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/util/relnode.c,v 1.32 2001/02/16 00:03:08 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -152,6 +152,7 @@ find_join_rel(Query *root, Relids relids) * * 'outer_rel' and 'inner_rel' are relation nodes for the relations to be * joined + * 'jointype': type of join (inner/outer) * 'restrictlist_ptr': result variable. If not NULL, *restrictlist_ptr * receives the list of RestrictInfo nodes that apply to this * particular pair of joinable relations. @@ -163,6 +164,7 @@ RelOptInfo * get_join_rel(Query *root, RelOptInfo *outer_rel, RelOptInfo *inner_rel, + JoinType jointype, List **restrictlist_ptr) { List *joinrelids; @@ -252,7 +254,7 @@ get_join_rel(Query *root, * Set estimates of the joinrel's size. */ set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel, - restrictlist); + jointype, restrictlist); /* * Add the joinrel to the query's joinrel list. diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h index c6dfcac39c..5caa576f0c 100644 --- a/src/include/optimizer/cost.h +++ b/src/include/optimizer/cost.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: cost.h,v 1.37 2001/01/24 19:43:26 momjian Exp $ + * $Id: cost.h,v 1.38 2001/02/16 00:03:05 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -70,6 +70,7 @@ extern void set_baserel_size_estimates(Query *root, RelOptInfo *rel); extern void set_joinrel_size_estimates(Query *root, RelOptInfo *rel, RelOptInfo *outer_rel, RelOptInfo *inner_rel, + JoinType jointype, List *restrictlist); /* diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h index b4e239aa8f..7e00003476 100644 --- a/src/include/optimizer/pathnode.h +++ b/src/include/optimizer/pathnode.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: pathnode.h,v 1.33 2001/01/24 19:43:26 momjian Exp $ + * $Id: pathnode.h,v 1.34 2001/02/16 00:03:06 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -66,8 +66,10 @@ extern HashPath *create_hashjoin_path(RelOptInfo *joinrel, */ extern RelOptInfo *get_base_rel(Query *root, int relid); extern RelOptInfo *make_base_rel(Query *root, int relid); -extern RelOptInfo *get_join_rel(Query *root, RelOptInfo *outer_rel, - RelOptInfo *inner_rel, - List **restrictlist_ptr); +extern RelOptInfo *get_join_rel(Query *root, + RelOptInfo *outer_rel, + RelOptInfo *inner_rel, + JoinType jointype, + List **restrictlist_ptr); #endif /* PATHNODE_H */