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Commite8140ad

Browse files
committed
Further sort-order twiddling in optimizer: be smart about
case where ORDER BY and GROUP BY request the same sort order.
1 parentc9d040d commite8140ad

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4 files changed

+97
-57
lines changed

4 files changed

+97
-57
lines changed

‎src/backend/optimizer/plan/createplan.c

Lines changed: 6 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.75 1999/08/2220:14:47 tgl Exp $
12+
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.76 1999/08/2223:56:44 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -51,7 +51,6 @@ static List *fix_indxqual_sublist(List *indexqual, IndexPath *index_path,
5151
Form_pg_indexindex);
5252
staticNode*fix_indxqual_operand(Node*node,IndexPath*index_path,
5353
Form_pg_indexindex);
54-
staticNoname*make_noname(List*tlist,List*pathkeys,Plan*plan_node);
5554
staticIndexScan*make_indexscan(List*qptlist,List*qpqual,Indexscanrelid,
5655
List*indxid,List*indxqual,List*indxqualorig);
5756
staticNestLoop*make_nestloop(List*qptlist,List*qpqual,Plan*lefttree,
@@ -926,12 +925,12 @@ copy_costsize(Plan *dest, Plan *src)
926925
* 'tlist' is the target list of the scan to be sorted or materialized
927926
* 'pathkeys' is the list of pathkeys by which the result is to be sorted
928927
*(NIL implies no sort needed, just materialize it)
929-
* 'plan_node' is the node which yields input tuples
928+
* 'subplan' is the node which yields input tuples
930929
*/
931-
staticNoname*
930+
Noname*
932931
make_noname(List*tlist,
933932
List*pathkeys,
934-
Plan*plan_node)
933+
Plan*subplan)
935934
{
936935
List*noname_tlist;
937936
intnumsortkeys;
@@ -946,15 +945,15 @@ make_noname(List *tlist,
946945
/* need to sort */
947946
retval= (Plan*)make_sort(noname_tlist,
948947
_NONAME_RELATION_ID_,
949-
plan_node,
948+
subplan,
950949
numsortkeys);
951950
}
952951
else
953952
{
954953
/* no sort */
955954
retval= (Plan*)make_material(noname_tlist,
956955
_NONAME_RELATION_ID_,
957-
plan_node,
956+
subplan,
958957
0);
959958
}
960959

‎src/backend/optimizer/plan/planmain.c

Lines changed: 30 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.42 1999/08/2220:14:48 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.43 1999/08/2223:56:45 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -44,11 +44,14 @@ static Plan *subplanner(Query *root, List *flat_tlist, List *qual);
4444
* qual is the qualification of the query
4545
*
4646
* Note: the Query node now also includes a query_pathkeys field, which
47+
* is both an input and an output of query_planner(). The input value
4748
* signals query_planner that the indicated sort order is wanted in the
48-
* final output plan. If, for some reason, query_planner is unable to
49-
* comply, it sets query_pathkeys to NIL before returning. (The reason
50-
* query_pathkeys is a Query field and not a passed parameter is that
51-
* the low-level routines in indxpath.c need to see it.)
49+
* final output plan. The output value is the actual pathkeys of the
50+
* selected path. This might not be the same as what the caller requested;
51+
* the caller must do pathkeys_contained_in() to decide whether an
52+
* explicit sort is still needed. (The main reason query_pathkeys is a
53+
* Query field and not a passed parameter is that the low-level routines
54+
* in indxpath.c need to see it.)
5255
*
5356
* Returns a query plan.
5457
*/
@@ -255,7 +258,11 @@ subplanner(Query *root,
255258
if (root->query_pathkeys==NIL||
256259
pathkeys_contained_in(root->query_pathkeys,
257260
final_rel->cheapestpath->pathkeys))
261+
{
262+
root->query_pathkeys=final_rel->cheapestpath->pathkeys;
258263
returncreate_plan(final_rel->cheapestpath);
264+
}
265+
259266
/*
260267
* Otherwise, look to see if we have an already-ordered path that is
261268
* cheaper than doing an explicit sort on cheapestpath.
@@ -271,6 +278,7 @@ subplanner(Query *root,
271278
if (sortedpath->path_cost <=cheapest_cost)
272279
{
273280
/* Found a better presorted path, use it */
281+
root->query_pathkeys=sortedpath->pathkeys;
274282
returncreate_plan(sortedpath);
275283
}
276284
/* otherwise, doing it the hard way is still cheaper */
@@ -300,21 +308,31 @@ subplanner(Query *root,
300308
* then poke the result.
301309
*/
302310
Plan*sortedplan=create_plan(sortedpath);
311+
List*sortedpathkeys;
303312

304313
Assert(IsA(sortedplan,IndexScan));
305314
((IndexScan*)sortedplan)->indxorderdir=BackwardScanDirection;
315+
/*
316+
* Need to generate commuted keys representing the actual
317+
* sort order. This should succeed, probably, but just in
318+
* case it does not, use the original root->query_pathkeys
319+
* as a conservative approximation.
320+
*/
321+
sortedpathkeys=copyObject(sortedpath->pathkeys);
322+
if (commute_pathkeys(sortedpathkeys))
323+
root->query_pathkeys=sortedpathkeys;
324+
306325
returnsortedplan;
307326
}
308327
}
309328
}
310329

311-
/* Nothing for it but to sort the cheapestpath...
312-
*
313-
*We indicate we failed to sort the plan, and let thecaller
314-
*stick the appropriate sort node on top. union_planner has to be
315-
*able to add a sort node anyway, so no need for extra code here.
330+
/* Nothing for it but to sort the cheapestpath --- but we let the
331+
* caller do that. union_planner has to be able to add a sort node
332+
*anyway, so no need for extra code here. (Furthermore, thegiven
333+
*pathkeys might involve something we can't compute yet, such as
334+
*an aggregate function...)
316335
*/
317-
root->query_pathkeys=NIL;/* sorry, it ain't sorted */
318-
336+
root->query_pathkeys=final_rel->cheapestpath->pathkeys;
319337
returncreate_plan(final_rel->cheapestpath);
320338
}

‎src/backend/optimizer/plan/planner.c

Lines changed: 59 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.64 1999/08/2220:14:48 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.65 1999/08/2223:56:45 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -39,7 +39,7 @@ static List *make_subplanTargetList(Query *parse, List *tlist,
3939
AttrNumber**groupColIdx);
4040
staticPlan*make_groupplan(List*group_tlist,booltuplePerGroup,
4141
List*groupClause,AttrNumber*grpColIdx,
42-
boolis_sorted,Plan*subplan);
42+
boolis_presorted,Plan*subplan);
4343
staticPlan*make_sortplan(List*tlist,List*sortcls,Plan*plannode);
4444

4545
/*****************************************************************************
@@ -91,7 +91,7 @@ union_planner(Query *parse)
9191
List*rangetable=parse->rtable;
9292
Plan*result_plan= (Plan*)NULL;
9393
AttrNumber*groupColIdx=NULL;
94-
boolis_sorted= false;
94+
List*current_pathkeys=NIL;
9595
Indexrt_index;
9696

9797
if (parse->unionClause)
@@ -102,6 +102,11 @@ union_planner(Query *parse)
102102
parse->commandType,
103103
parse->resultRelation,
104104
parse->rtable);
105+
/*
106+
* We leave current_pathkeys NIL indicating we do not know sort order.
107+
* Actually, for a normal UNION we have done an explicit sort; ought
108+
* to change interface to plan_union_queries to pass that info back!
109+
*/
105110
}
106111
elseif ((rt_index=first_inherit_rt_entry(rangetable))!=-1)
107112
{
@@ -135,6 +140,10 @@ union_planner(Query *parse)
135140

136141
if (parse->rowMark!=NULL)
137142
elog(ERROR,"SELECT FOR UPDATE is not supported for inherit queries");
143+
/*
144+
* We leave current_pathkeys NIL indicating we do not know sort order
145+
* of the Append-ed results.
146+
*/
138147
}
139148
else
140149
{
@@ -182,25 +191,25 @@ union_planner(Query *parse)
182191
}
183192
}
184193

194+
/*
195+
* Generate appropriate target list for subplan; may be different
196+
* from tlist if grouping or aggregation is needed.
197+
*/
198+
sub_tlist=make_subplanTargetList(parse,tlist,&groupColIdx);
199+
185200
/*
186201
* Figure out whether we need a sorted result from query_planner.
187202
*
188203
* If we have a GROUP BY clause, then we want a result sorted
189-
* properly for grouping. Otherwise, if there is an ORDER BY clause
190-
* and no need for an aggregate node, we want to sort by the ORDER BY
191-
* clause. (XXX In some cases, we could presort even when there is
192-
* an aggregate, but I'll leave that refinement for another day.)
193-
*
194-
* NOTE: the reason we put the target pathkeys into the Query node
195-
* rather than passing them as an argument to query_planner is that
196-
* the low-level routines in indxpath.c want to be able to see them.
204+
* properly for grouping. Otherwise, if there is an ORDER BY clause,
205+
* we want to sort by the ORDER BY clause.
197206
*/
198207
if (parse->groupClause)
199208
{
200209
parse->query_pathkeys=
201210
make_pathkeys_for_sortclauses(parse->groupClause,tlist);
202211
}
203-
elseif (parse->sortClause&& !parse->hasAggs)
212+
elseif (parse->sortClause)
204213
{
205214
parse->query_pathkeys=
206215
make_pathkeys_for_sortclauses(parse->sortClause,tlist);
@@ -210,23 +219,16 @@ union_planner(Query *parse)
210219
parse->query_pathkeys=NIL;
211220
}
212221

213-
/*
214-
* Generate appropriate target list for subplan; may be different
215-
* from tlist if grouping or aggregation is needed.
216-
*/
217-
sub_tlist=make_subplanTargetList(parse,tlist,&groupColIdx);
218-
219222
/* Generate the (sub) plan */
220223
result_plan=query_planner(parse,
221224
parse->commandType,
222225
sub_tlist,
223226
(List*)parse->qual);
224227

225-
/* query_plannersets query_pathkeys to NIL if it didn't make
226-
*a properly sorted plan
228+
/* query_plannerreturns actual sort order (which is not
229+
*necessarily what we requested) in query_pathkeys.
227230
*/
228-
if (parse->query_pathkeys)
229-
is_sorted= true;
231+
current_pathkeys=parse->query_pathkeys;
230232
}
231233

232234
/* query_planner returns NULL if it thinks plan is bogus */
@@ -241,6 +243,8 @@ union_planner(Query *parse)
241243
{
242244
booltuplePerGroup;
243245
List*group_tlist;
246+
List*group_pathkeys;
247+
boolis_sorted;
244248

245249
/*
246250
* Decide whether how many tuples per group the Group node needs
@@ -261,18 +265,33 @@ union_planner(Query *parse)
261265
else
262266
group_tlist=tlist;
263267

268+
/*
269+
* Figure out whether the path result is already ordered the way we
270+
* need it --- if so, no need for an explicit sort step.
271+
*/
272+
group_pathkeys=make_pathkeys_for_sortclauses(parse->groupClause,
273+
tlist);
274+
if (pathkeys_contained_in(group_pathkeys,current_pathkeys))
275+
{
276+
is_sorted= true;/* no sort needed now */
277+
/* current_pathkeys remains unchanged */
278+
}
279+
else
280+
{
281+
/* We will need to do an explicit sort by the GROUP BY clause.
282+
* make_groupplan will do the work, but set current_pathkeys
283+
* to indicate the resulting order.
284+
*/
285+
is_sorted= false;
286+
current_pathkeys=group_pathkeys;
287+
}
288+
264289
result_plan=make_groupplan(group_tlist,
265290
tuplePerGroup,
266291
parse->groupClause,
267292
groupColIdx,
268293
is_sorted,
269294
result_plan);
270-
271-
/*
272-
* Assume the result of the group step is not ordered suitably
273-
* for any ORDER BY that may exist. XXX it might be; improve this!
274-
*/
275-
is_sorted= false;
276295
}
277296

278297
/*
@@ -325,20 +344,23 @@ union_planner(Query *parse)
325344
/* HAVING clause, if any, becomes qual of the Agg node */
326345
result_plan->qual= (List*)parse->havingQual;
327346

328-
/*
329-
* Assume result is not ordered suitably for ORDER BY.
330-
* XXX it might be; improve this!
331-
*/
332-
is_sorted= false;
347+
/* Note: Agg does not affect any existing sort order of the tuples */
333348
}
334349

335350
/*
336351
* If we were not able to make the plan come out in the right order,
337352
* add an explicit sort step.
338353
*/
339-
if (parse->sortClause&& !is_sorted)
354+
if (parse->sortClause)
340355
{
341-
result_plan=make_sortplan(tlist,parse->sortClause,result_plan);
356+
List*sort_pathkeys;
357+
358+
sort_pathkeys=make_pathkeys_for_sortclauses(parse->sortClause,
359+
tlist);
360+
if (!pathkeys_contained_in(sort_pathkeys,current_pathkeys))
361+
{
362+
result_plan=make_sortplan(tlist,parse->sortClause,result_plan);
363+
}
342364
}
343365

344366
/*
@@ -474,12 +496,12 @@ make_groupplan(List *group_tlist,
474496
booltuplePerGroup,
475497
List*groupClause,
476498
AttrNumber*grpColIdx,
477-
boolis_sorted,
499+
boolis_presorted,
478500
Plan*subplan)
479501
{
480502
intnumCols=length(groupClause);
481503

482-
if (!is_sorted)
504+
if (!is_presorted)
483505
{
484506
/*
485507
* The Sort node always just takes a copy of the subplan's tlist

‎src/include/optimizer/planmain.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
*
77
* Copyright (c) 1994, Regents of the University of California
88
*
9-
* $Id: planmain.h,v 1.32 1999/08/2220:14:56 tgl Exp $
9+
* $Id: planmain.h,v 1.33 1999/08/2223:56:43 tgl Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -33,6 +33,7 @@ extern Sort *make_sort(List *tlist, Oid nonameid, Plan *lefttree,
3333
externAgg*make_agg(List*tlist,Plan*lefttree);
3434
externGroup*make_group(List*tlist,booltuplePerGroup,intngrp,
3535
AttrNumber*grpColIdx,Plan*lefttree);
36+
externNoname*make_noname(List*tlist,List*pathkeys,Plan*subplan);
3637
externUnique*make_unique(List*tlist,Plan*lefttree,char*uniqueAttr);
3738
externResult*make_result(List*tlist,Node*resconstantqual,Plan*subplan);
3839

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