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Implement subselects in target lists. Also, relax requirement that

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subselects can only appear on the righthand side of a binary operator.
That's still true for quantified predicates like x = ANY (SELECT ...),
but a subselect that delivers a single result can now appear anywhere
in an expression.  This is implemented by changing EXPR_SUBLINK sublinks
to represent just the (SELECT ...) expression, without any 'left hand
side' or combining operator --- so they're now more like EXISTS_SUBLINK.
To handle the case of '(x, y, z) = (SELECT ...)', I added a new sublink
type MULTIEXPR_SUBLINK, which acts just like EXPR_SUBLINK used to.
But the grammar will only generate one for a multiple-left-hand-side
row expression.
This commit is contained in:
Tom Lane
1999-11-15 02:00:15 +00:00
parent 1ecb129d20
commit f68e11f373
12 changed files with 364 additions and 566 deletions
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18
src/backend/optimizer/plan/planmain.c
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@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.46 1999/10/07 04:23:06 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.47 1999/11/15 02:00:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -87,9 +87,25 @@ query_planner(Query *root,
tlist = (List *) SS_replace_correlation_vars((Node *) tlist);
qual = (List *) SS_replace_correlation_vars((Node *) qual);
}
/* Expand SubLinks to SubPlans */
if (root->hasSubLinks)
{
tlist = (List *) SS_process_sublinks((Node *) tlist);
qual = (List *) SS_process_sublinks((Node *) qual);
if (root->groupClause != NIL)
{
/*
* Check for ungrouped variables passed to subplans.
* Note we do NOT do this for subplans in WHERE; it's legal
* there because WHERE is evaluated pre-GROUP.
*/
if (check_subplans_for_ungrouped_vars((Node *) tlist,
root->groupClause,
tlist))
elog(ERROR, "Sub-SELECT must use only GROUPed attributes from outer SELECT");
}
}
/*
* If the query contains no relation references at all, it must be