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Commit0eb5ab8

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Apply a MATERIAL node to the result of an uncorrelated subplan, if it
looks like it will save computation to do so.
1 parent9f19842 commit0eb5ab8

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1 file changed

+71
-5
lines changed

1 file changed

+71
-5
lines changed

‎src/backend/optimizer/plan/subselect.c

Lines changed: 71 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.28 2000/02/15 20:49:18 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.29 2000/03/02 04:08:16 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -18,6 +18,8 @@
1818
#include"nodes/makefuncs.h"
1919
#include"nodes/nodeFuncs.h"
2020
#include"optimizer/clauses.h"
21+
#include"optimizer/cost.h"
22+
#include"optimizer/planmain.h"
2123
#include"optimizer/planner.h"
2224
#include"optimizer/subselect.h"
2325
#include"parser/parse_expr.h"
@@ -123,6 +125,7 @@ static Node *
123125
make_subplan(SubLink*slink)
124126
{
125127
SubPlan*node=makeNode(SubPlan);
128+
Query*subquery= (Query*) (slink->subselect);
126129
doubletuple_fraction;
127130
Plan*plan;
128131
List*lst;
@@ -151,8 +154,7 @@ make_subplan(SubLink *slink)
151154
else
152155
tuple_fraction=0.5;/* 50% */
153156

154-
node->plan=plan=union_planner((Query*)slink->subselect,
155-
tuple_fraction);
157+
node->plan=plan=union_planner(subquery,tuple_fraction);
156158

157159
/*
158160
* Assign subPlan, extParam and locParam to plan nodes. At the moment,
@@ -179,7 +181,7 @@ make_subplan(SubLink *slink)
179181
PlannerQueryLevel--;
180182

181183
node->plan_id=PlannerPlanId++;
182-
node->rtable=((Query*)slink->subselect)->rtable;
184+
node->rtable=subquery->rtable;
183185
node->sublink=slink;
184186
slink->subselect=NULL;/* cool ?! */
185187

@@ -287,12 +289,76 @@ make_subplan(SubLink *slink)
287289
}
288290
else
289291
{
290-
/* make expression of SUBPLAN type */
291292
Expr*expr=makeNode(Expr);
292293
List*args=NIL;
293294
List*newoper=NIL;
294295
inti=0;
295296

297+
/*
298+
* We can't convert subplans of ALL_SUBLINK or ANY_SUBLINK types to
299+
* initPlans, even when they are uncorrelated or undirect correlated,
300+
* because we need to scan the output of the subplan for each outer
301+
* tuple. However, we have the option to tack a MATERIAL node onto
302+
* the top of an uncorrelated/undirect correlated subplan, which lets
303+
* us do the work of evaluating the subplan only once. We do this
304+
* if the subplan's top plan node is anything more complicated than
305+
* a sequential or index scan, and we do it even for those plan types
306+
* if the qual appears selective enough to eliminate many tuples.
307+
*/
308+
if (node->parParam==NIL)
309+
{
310+
booluse_material;
311+
312+
switch (nodeTag(plan))
313+
{
314+
caseT_SeqScan:
315+
{
316+
Selectivityqualsel;
317+
318+
qualsel=clauselist_selectivity(subquery,plan->qual,0);
319+
/* Is 10% selectivity a good threshold?? */
320+
use_material=qualsel<0.10;
321+
break;
322+
}
323+
caseT_IndexScan:
324+
{
325+
List*indxqual= ((IndexScan*)plan)->indxqualorig;
326+
Selectivityqualsel;
327+
328+
qualsel=clauselist_selectivity(subquery,plan->qual,0);
329+
qualsel *=clauselist_selectivity(subquery,indxqual,0);
330+
/* Note: if index is lossy, we just double-counted the
331+
* index selectivity. Worth fixing?
332+
*/
333+
/* Is 10% selectivity a good threshold?? */
334+
use_material=qualsel<0.10;
335+
break;
336+
}
337+
caseT_Material:
338+
caseT_Sort:
339+
/* Don't add another Material node if there's one already,
340+
* nor if the top node is a Sort, since Sort materializes
341+
* its output anyway. (I doubt either case can happen in
342+
* practice for a subplan, but...)
343+
*/
344+
use_material= false;
345+
break;
346+
default:
347+
use_material= true;
348+
break;
349+
}
350+
if (use_material)
351+
{
352+
plan= (Plan*)make_noname(plan->targetlist,
353+
NIL,
354+
plan);
355+
node->plan=plan;
356+
}
357+
}
358+
359+
/*
360+
* Make expression of SUBPLAN type
361+
*/
296362
expr->typeOid=BOOLOID;/* bogus, but we don't really care */
297363
expr->opType=SUBPLAN_EXPR;
298364
expr->oper= (Node*)node;

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