database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-17 06:41:09 +03:00
Code Activity

Allow merge and hash joins to occur on arbitrary expressions (anything not

Browse Source 
containing a volatile function), rather than only on 'Var = Var' clauses
as before.  This makes it practical to do flatten_join_alias_vars at the
start of planning, which in turn eliminates a bunch of klugery inside the
planner to deal with alias vars.  As a free side effect, we now detect
implied equality of non-Var expressions; for example in
	SELECT ... WHERE a.x = b.y and b.y = 42
we will deduce a.x = 42 and use that as a restriction qual on a.  Also,
we can remove the restriction introduced 12/5/02 to prevent pullup of
subqueries whose targetlists contain sublinks.
Still TODO: make statistical estimation routines in selfuncs.c and costsize.c
smarter about expressions that are more complex than plain Vars.  The need
for this is considerably greater now that we have to be able to estimate
the suitability of merge and hash join techniques on such expressions.
This commit is contained in:
Tom Lane
2003-01-15 19:35:48 +00:00
parent 0eed62f34d
commit de97072e3c
32 changed files with 523 additions and 662 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
src/backend/optimizer/path/pathkeys.c
View File

@ -11,7 +11,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.43 2002/12/17 01:18:22 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.44 2003/01/15 19:35:40 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -53,27 +53,23 @@ makePathKeyItem(Node *key, Oid sortop)
* The given clause has a mergejoinable operator, so its two sides
* can be considered equal after restriction clause application; in
* particular, any pathkey mentioning one side (with the correct sortop)
* can be expanded to include the other as well. Record the vars and
* can be expanded to include the other as well. Record the exprs and
* associated sortops in the query's equi_key_list for future use.
*
* The query's equi_key_list field points to a list of sublists of PathKeyItem
* nodes, where each sublist is a set of two or more vars+sortops that have
* nodes, where each sublist is a set of two or more exprs+sortops that have
* been identified as logically equivalent (and, therefore, we may consider
* any two in a set to be equal). As described above, we will subsequently
* use direct pointers to one of these sublists to represent any pathkey
* that involves an equijoined variable.
*
* This code would actually work fine with expressions more complex than
* a single Var, but currently it won't see any because check_mergejoinable
* won't accept such clauses as mergejoinable.
*/
void
add_equijoined_keys(Query *root, RestrictInfo *restrictinfo)
{
Expr *clause = restrictinfo->clause;
PathKeyItem *item1 = makePathKeyItem((Node *) get_leftop(clause),
PathKeyItem *item1 = makePathKeyItem(get_leftop(clause),
restrictinfo->left_sortop);
PathKeyItem *item2 = makePathKeyItem((Node *) get_rightop(clause),
PathKeyItem *item2 = makePathKeyItem(get_rightop(clause),
restrictinfo->right_sortop);
List *newset,
*cursetlink;
@ -717,13 +713,13 @@ cache_mergeclause_pathkeys(Query *root, RestrictInfo *restrictinfo)
if (restrictinfo->left_pathkey == NIL)
{
key = (Node *) get_leftop(restrictinfo->clause);
key = get_leftop(restrictinfo->clause);
item = makePathKeyItem(key, restrictinfo->left_sortop);
restrictinfo->left_pathkey = make_canonical_pathkey(root, item);
}
if (restrictinfo->right_pathkey == NIL)
{
key = (Node *) get_rightop(restrictinfo->clause);
key = get_rightop(restrictinfo->clause);
item = makePathKeyItem(key, restrictinfo->right_sortop);
restrictinfo->right_pathkey = make_canonical_pathkey(root, item);
}
@ -852,32 +848,24 @@ make_pathkeys_for_mergeclauses(Query *root,
foreach(i, mergeclauses)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(i);
Node *key;
List *pathkey;
cache_mergeclause_pathkeys(root, restrictinfo);
key = (Node *) get_leftop(restrictinfo->clause);
if (IsA(key, Var) &&
VARISRELMEMBER(((Var *) key)->varno, rel))
if (is_subseti(restrictinfo->left_relids, rel->relids))
{
/* Rel is left side of mergeclause */
pathkey = restrictinfo->left_pathkey;
}
else if (is_subseti(restrictinfo->right_relids, rel->relids))
{
/* Rel is right side of mergeclause */
pathkey = restrictinfo->right_pathkey;
}
else
{
key = (Node *) get_rightop(restrictinfo->clause);
if (IsA(key, Var) &&
VARISRELMEMBER(((Var *) key)->varno, rel))
{
/* Rel is right side of mergeclause */
pathkey = restrictinfo->right_pathkey;
}
else
{
elog(ERROR, "make_pathkeys_for_mergeclauses: can't identify which side of mergeclause to use");
pathkey = NIL; /* keep compiler quiet */
}
elog(ERROR, "make_pathkeys_for_mergeclauses: can't identify which side of mergeclause to use");
pathkey = NIL; /* keep compiler quiet */
}
/*