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Fix oversight in planning of GROUP queries: when an expression is used

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as both a GROUP BY item and an output expression, the top-level Group
node should just copy up the evaluated expression value from its input,
rather than re-evaluating the expression.  Aside from any performance
benefit this might offer, this avoids a crash when there is a sub-SELECT
in said expression.
This commit is contained in:
Tom Lane
2001-01-09 03:48:51 +00:00
parent 4cb0950cfe
commit 07c741e61c
4 changed files with 67 additions and 12 deletions
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66
src/backend/optimizer/plan/setrefs.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.68 2000/10/26 21:36:09 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.69 2001/01/09 03:48:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -17,6 +17,7 @@
#include "postgres.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/planmain.h"
@ -270,22 +271,75 @@ set_join_references(Join *join)
* to refer to the tuples returned by its lefttree subplan.
*
* This is used for single-input plan types like Agg, Group, Result.
*
* In most cases, we have to match up individual Vars in the tlist and
* qual expressions with elements of the subplan's tlist (which was
* generated by flatten_tlist() from these selfsame expressions, so it
* should have all the required variables). There is an important exception,
* however: a GROUP BY expression that is also an output expression will
* have been pushed into the subplan tlist unflattened. We want to detect
* this case and reference the subplan output directly. Therefore, check
* for equality of the whole tlist expression to any subplan element before
* we resort to picking the expression apart for individual Vars.
*/
static void
set_uppernode_references(Plan *plan, Index subvarno)
{
Plan *subplan = plan->lefttree;
List *subplanTargetList;
List *subplanTargetList,
*outputTargetList,
*l;
if (subplan != NULL)
subplanTargetList = subplan->targetlist;
else
subplanTargetList = NIL;
plan->targetlist = (List *)
replace_vars_with_subplan_refs((Node *) plan->targetlist,
subvarno,
subplanTargetList);
outputTargetList = NIL;
foreach (l, plan->targetlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
TargetEntry *subplantle;
Node *newexpr;
subplantle = tlistentry_member(tle->expr, subplanTargetList);
if (subplantle)
{
/* Found a matching subplan output expression */
Resdom *resdom = subplantle->resdom;
Var *newvar;
newvar = makeVar(subvarno,
resdom->resno,
resdom->restype,
resdom->restypmod,
0);
/* If we're just copying a simple Var, copy up original info */
if (subplantle->expr && IsA(subplantle->expr, Var))
{
Var *subvar = (Var *) subplantle->expr;
newvar->varnoold = subvar->varnoold;
newvar->varoattno = subvar->varoattno;
}
else
{
newvar->varnoold = 0;
newvar->varoattno = 0;
}
newexpr = (Node *) newvar;
}
else
{
/* No matching expression, so replace individual Vars */
newexpr = replace_vars_with_subplan_refs(tle->expr,
subvarno,
subplanTargetList);
}
outputTargetList = lappend(outputTargetList,
makeTargetEntry(tle->resdom, newexpr));
}
plan->targetlist = outputTargetList;
plan->qual = (List *)
replace_vars_with_subplan_refs((Node *) plan->qual,