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Tweak trivial_subqueryscan() to consider a SubqueryScan's targetlist

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trivial if it contains either Vars referencing the corresponding subplan
columns, or Consts equaling the corresponding subplan columns.  This
lets the planner eliminate the SubqueryScan in some cases generated by
generate_setop_tlist().
This commit is contained in:
Tom Lane 2006-08-28 14:32:41 +00:00
parent 88b8110443
commit fcba3b82e2
1 changed files with 24 additions and 8 deletions
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24
src/backend/optimizer/plan/setrefs.c
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@ -9,7 +9,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/setrefs.c,v 1.124 2006/08/12 02:52:05 tgl Exp $ * $PostgreSQL: pgsql/src/backend/optimizer/plan/setrefs.c,v 1.125 2006/08/28 14:32:41 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -448,16 +448,32 @@ trivial_subqueryscan(SubqueryScan *plan)
{ {
TargetEntry *ptle = (TargetEntry *) lfirst(lp); TargetEntry *ptle = (TargetEntry *) lfirst(lp);
TargetEntry *ctle = (TargetEntry *) lfirst(lc); TargetEntry *ctle = (TargetEntry *) lfirst(lc);
Var *var = (Var *) ptle->expr;
if (ptle->resjunk != ctle->resjunk) if (ptle->resjunk != ctle->resjunk)
return false; /* tlist doesn't match junk status */ return false; /* tlist doesn't match junk status */
if (!var || !IsA(var, Var))
return false; /* tlist item not a Var */ /*
* We accept either a Var referencing the corresponding element of
* the subplan tlist, or a Const equaling the subplan element.
* See generate_setop_tlist() for motivation.
*/
if (ptle->expr && IsA(ptle->expr, Var))
{
Var *var = (Var *) ptle->expr;
Assert(var->varno == plan->scan.scanrelid); Assert(var->varno == plan->scan.scanrelid);
Assert(var->varlevelsup == 0); Assert(var->varlevelsup == 0);
if (var->varattno != attrno) if (var->varattno != attrno)
return false; /* out of order */ return false; /* out of order */
}
else if (ptle->expr && IsA(ptle->expr, Const))
{
if (!equal(ptle->expr, ctle->expr))
return false;
}
else
return false;
attrno++; attrno++;
} }