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Commite35e6b1

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committed
Back out prior patch and instead just suppress SubqueryScan elimination
when there are extra resjunk columns in the child node. I found someadditional cases involving Append nodes that weren't handled by theprior patch, and it's not clear how to fix them in the same way withoutbreaking inheritance cases. So the prudent path seems to be to narrowthe scope of the optimization.
1 parent2da2d34 commite35e6b1

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1 file changed

+16
-40
lines changed

1 file changed

+16
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‎src/backend/optimizer/plan/setrefs.c‎

Lines changed: 16 additions & 40 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/optimizer/plan/setrefs.c,v 1.113 2005/09/0517:25:01 tgl Exp $
12+
* $PostgreSQL: pgsql/src/backend/optimizer/plan/setrefs.c,v 1.114 2005/09/0518:59:38 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -130,7 +130,6 @@ static void set_sa_opfuncid(ScalarArrayOpExpr *opexpr);
130130
Plan*
131131
set_plan_references(Plan*plan,List*rtable)
132132
{
133-
boolcopy_lefttree_tlist= false;
134133
ListCell*l;
135134

136135
if (plan==NULL)
@@ -219,13 +218,14 @@ set_plan_references(Plan *plan, List *rtable)
219218

220219
/*
221220
* These plan types don't actually bother to evaluate their
222-
* targetlists, because they just return their unmodified
223-
* input tuples; so their targetlists should just be copies
224-
* of their input plan nodes' targetlists. The actual copying
225-
* has to be done after we've finalized the input node.
226-
*/
227-
copy_lefttree_tlist= true;
228-
/*
221+
* targetlists (because they just return their unmodified
222+
* input tuples). The optimizer is lazy about creating really
223+
* valid targetlists for them --- it tends to just put in a
224+
* pointer to the child plan node's tlist. Hence, we leave
225+
* the tlist alone. In particular, we do not want to process
226+
* subplans in the tlist, since we will likely end up reprocessing
227+
* subplans that also appear in lower levels of the plan tree!
228+
*
229229
* Since these plan types don't check quals either, we should
230230
* not find any qual expression attached to them.
231231
*/
@@ -238,7 +238,6 @@ set_plan_references(Plan *plan, List *rtable)
238238
* or quals. It does have live expressions for limit/offset,
239239
* however.
240240
*/
241-
copy_lefttree_tlist= true;
242241
Assert(plan->qual==NIL);
243242
fix_expr_references(plan, ((Limit*)plan)->limitOffset);
244243
fix_expr_references(plan, ((Limit*)plan)->limitCount);
@@ -267,10 +266,9 @@ set_plan_references(Plan *plan, List *rtable)
267266

268267
/*
269268
* Append, like Sort et al, doesn't actually evaluate its
270-
* targetlist or check quals, so don't fix targetlist/qual.
271-
* But do recurse into child plans. (Unlike Sort et al, the
272-
* correct tlist was made by createplan.c and we shouldn't
273-
* replace it.)
269+
* targetlist or check quals, and we haven't bothered to give it
270+
* its own tlist copy. So, don't fix targetlist/qual. But do
271+
* recurse into child plans.
274272
*/
275273
Assert(plan->qual==NIL);
276274
foreach(l, ((Append*)plan)->appendplans)
@@ -317,20 +315,6 @@ set_plan_references(Plan *plan, List *rtable)
317315
sp->plan=set_plan_references(sp->plan,sp->rtable);
318316
}
319317

320-
/*
321-
* If this is a non-projecting plan node, create a minimally valid
322-
* targetlist for it. Someday we might need to make this look really
323-
* real, with Vars referencing the input node's outputs, but for now
324-
* the executor only cares that the tlist has the right TargetEntry
325-
* fields (resname, resjunk etc) and exprType results. So we can
326-
* get away with just copying the input node's tlist. (Note:
327-
* createplan.c already did copy the input, but we have to do it
328-
* over in case we removed a SubqueryScan node: the new input plan
329-
* node might have extra resjunk fields.)
330-
*/
331-
if (copy_lefttree_tlist)
332-
plan->targetlist=copyObject(plan->lefttree->targetlist);
333-
334318
returnplan;
335319
}
336320

@@ -430,6 +414,10 @@ trivial_subqueryscan(SubqueryScan *plan)
430414
if (plan->scan.plan.qual!=NIL)
431415
return false;
432416

417+
if (list_length(plan->scan.plan.targetlist)!=
418+
list_length(plan->subplan->targetlist))
419+
return false;/* tlists not same length */
420+
433421
attrno=1;
434422
forboth(lp,plan->scan.plan.targetlist,lc,plan->subplan->targetlist)
435423
{
@@ -448,18 +436,6 @@ trivial_subqueryscan(SubqueryScan *plan)
448436
attrno++;
449437
}
450438

451-
if (lp)
452-
return false;/* parent tlist longer than child */
453-
454-
/* extra child items are OK only if all are resjunk */
455-
for_each_cell(lc,lc)
456-
{
457-
TargetEntry*ctle= (TargetEntry*)lfirst(lc);
458-
459-
if (!ctle->resjunk)
460-
return false;
461-
}
462-
463439
return true;
464440
}
465441

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