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

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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
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21
src/backend/utils/adt/selfuncs.c
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@@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.125 2003/01/12 22:35:29 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.126 2003/01/15 19:35:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1754,8 +1754,8 @@ mergejoinscansel(Query *root, Node *clause,
if (!is_opclause(clause))
return; /* shouldn't happen */
opno = ((OpExpr *) clause)->opno;
left = get_leftop((Expr *) clause);
right = get_rightop((Expr *) clause);
left = (Var *) get_leftop((Expr *) clause);
right = (Var *) get_rightop((Expr *) clause);
if (!right)
return; /* shouldn't happen */
@@ -1766,8 +1766,6 @@ mergejoinscansel(Query *root, Node *clause,
/* Verify mergejoinability and get left and right "<" operators */
if (!op_mergejoinable(opno,
left->vartype,
right->vartype,
&lsortop,
&rsortop))
return; /* shouldn't happen */
@@ -1892,17 +1890,6 @@ estimate_num_groups(Query *root, List *groupClauses, double input_rows)
List *varshere;
varshere = pull_var_clause(groupexpr, false);
/*
* Replace any JOIN alias Vars with the underlying Vars. (This
* is not really right for FULL JOIN ...)
*/
if (root->hasJoinRTEs)
{
varshere = (List *) flatten_join_alias_vars((Node *) varshere,
root->rtable,
true);
varshere = pull_var_clause((Node *) varshere, false);
}
/*
* If we find any variable-free GROUP BY item, then either it is
* a constant (and we can ignore it) or it contains a volatile
@@ -1963,7 +1950,7 @@ estimate_num_groups(Query *root, List *groupClauses, double input_rows)
l2 = lnext(l2);
if (var->varno != varinfo->var->varno &&
vars_known_equal(root, var, varinfo->var))
exprs_known_equal(root, (Node *) var, (Node *) varinfo->var))
{
/* Found a match */
if (varinfo->ndistinct <= ndistinct)