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Commit605d849

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Clean up cost_sort some more: most callers were double-counting
the cost of reading the source data.
1 parent87d95ca commit605d849

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4 files changed

+20
-26
lines changed

4 files changed

+20
-26
lines changed

‎src/backend/optimizer/path/costsize.c

Lines changed: 13 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.35 1999/04/30 04:01:44 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.36 1999/05/01 19:47:41 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -167,28 +167,23 @@ cost_index(Oid indexid,
167167
/*
168168
* cost_sort
169169
* Determines and returns the cost of sorting a relation by considering
170-
*1.the cost of doing an external sort:XXX this is probably too low
170+
* the cost of doing an external sort:XXX this is probably too low
171171
*disk = (p lg p)
172172
*cpu = *CPU-PAGE-WEIGHT* * (t lg t)
173-
* 2. the cost of reading the sort result into memory (another seqscan)
174-
* unless 'noread' is set
175173
*
176174
* 'pathkeys' is a list of sort keys
177175
* 'tuples' is the number of tuples in the relation
178176
* 'width' is the average tuple width in bytes
179-
* 'noread' is a flag indicating that the cost of reading the sort
180-
*source data should not be included (i.e., the caller
181-
*will account for it separately).
182177
*
183178
* NOTE: some callers currently pass NULL for pathkeys because they
184-
* can't conveniently supply sort keys. Since this routine doesn't
179+
* can't conveniently supplythesort keys. Since this routine doesn't
185180
* currently do anything with pathkeys anyway, that doesn't matter...
181+
* but if it ever does, it should react gracefully to lack of key data.
186182
*
187183
* Returns a flonum.
188-
*
189184
*/
190185
Cost
191-
cost_sort(List*pathkeys,inttuples,intwidth,boolnoread)
186+
cost_sort(List*pathkeys,inttuples,intwidth)
192187
{
193188
Costtemp=0;
194189
intnpages=page_size(tuples,width);
@@ -200,6 +195,8 @@ cost_sort(List *pathkeys, int tuples, int width, bool noread)
200195
/* We want to be sure the cost of a sort is never estimated as zero,
201196
* even if passed-in tuple count is zero. Besides, mustn't do log(0)...
202197
*/
198+
if (tuples <=0)
199+
tuples=1;
203200
if (npages <=0)
204201
npages=1;
205202

@@ -210,13 +207,10 @@ cost_sort(List *pathkeys, int tuples, int width, bool noread)
210207
temp+=npages*log_npages;
211208

212209
/*
213-
* could be base_log(pages, NBuffers), but we are only doing 2-way
210+
* could be base_log(tuples, NBuffers), but we are only doing 2-way
214211
* merges
215212
*/
216-
temp+=_cpu_page_wight_*tuples*log_npages;
217-
218-
if (!noread)
219-
temp+=cost_seqscan(_NONAME_RELATION_ID_,npages,tuples);
213+
temp+=_cpu_page_wight_*tuples*base_log((double)tuples,2.0);
220214

221215
Assert(temp>0);
222216

@@ -282,7 +276,8 @@ cost_nestloop(Cost outercost,
282276
* 'outercost' and 'innercost' are the (disk+cpu) costs of scanning the
283277
*outer and inner relations
284278
* 'outersortkeys' and 'innersortkeys' are lists of the keys to be used
285-
*to sort the outer and inner relations
279+
*to sort the outer and inner relations (or NIL if no explicit
280+
*sort is needed because the source path is already ordered)
286281
* 'outertuples' and 'innertuples' are the number of tuples in the outer
287282
*and inner relations
288283
* 'outerwidth' and 'innerwidth' are the (typical) widths (in bytes)
@@ -309,9 +304,9 @@ cost_mergejoin(Cost outercost,
309304
temp+=outercost;
310305
temp+=innercost;
311306
if (outersortkeys)/* do we need to sort? */
312-
temp+=cost_sort(outersortkeys,outersize,outerwidth, true);
307+
temp+=cost_sort(outersortkeys,outersize,outerwidth);
313308
if (innersortkeys)/* do we need to sort? */
314-
temp+=cost_sort(innersortkeys,innersize,innerwidth, true);
309+
temp+=cost_sort(innersortkeys,innersize,innerwidth);
315310
temp+=_cpu_page_wight_* (outersize+innersize);
316311

317312
Assert(temp >=0);

‎src/backend/optimizer/path/joinpath.c

Lines changed: 3 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.33 1999/04/03 00:18:28 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.34 1999/05/01 19:47:42 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -348,7 +348,7 @@ match_unsorted_outer(RelOptInfo *joinrel,
348348
(mergeinnerpath->path_cost<
349349
(cheapest_inner->path_cost+
350350
cost_sort(matchedJoinKeys,innerrel->size,
351-
innerrel->width, false))));
351+
innerrel->width))));
352352
if (!path_is_cheaper_than_sort)
353353
{
354354
varkeys=make_pathkeys_from_joinkeys(matchedJoinKeys,
@@ -464,8 +464,7 @@ match_unsorted_inner(RelOptInfo *joinrel,
464464
if (clauses&&matchedJoinKeys)
465465
{
466466
temp1=outerrel->cheapestpath->path_cost+
467-
cost_sort(matchedJoinKeys,outerrel->size,outerrel->width,
468-
false);
467+
cost_sort(matchedJoinKeys,outerrel->size,outerrel->width);
469468

470469
temp2= (bool) (FLOAT_IS_ZERO(innerpath->outerjoincost)
471470
|| (innerpath->outerjoincost>temp1));

‎src/backend/optimizer/plan/createplan.c

Lines changed: 2 additions & 2 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/createplan.c,v 1.51 1999/04/30 04:04:27 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.52 1999/05/01 19:47:40 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -1106,7 +1106,7 @@ make_sort(List *tlist, Oid nonameid, Plan *lefttree, int keycount)
11061106
Plan*plan=&node->plan;
11071107

11081108
copy_costsize(plan,lefttree);
1109-
plan->cost+=cost_sort(NULL,plan->plan_size,plan->plan_width, true);
1109+
plan->cost+=cost_sort(NULL,plan->plan_size,plan->plan_width);
11101110
plan->state= (EState*)NULL;
11111111
plan->targetlist=tlist;
11121112
plan->qual=NIL;

‎src/include/optimizer/cost.h

Lines changed: 2 additions & 2 deletions
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: cost.h,v 1.17 1999/02/13 23:21:43 momjian Exp $
9+
* $Id: cost.h,v 1.18 1999/05/01 19:47:39 tgl Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -34,7 +34,7 @@ extern Cost cost_seqscan(int relid, int relpages, int reltuples);
3434
externCostcost_index(Oidindexid,intexpected_indexpages,Costselec,
3535
intrelpages,intreltuples,intindexpages,
3636
intindextuples,boolis_injoin);
37-
externCostcost_sort(List*pathkeys,inttuples,intwidth,boolnoread);
37+
externCostcost_sort(List*pathkeys,inttuples,intwidth);
3838
externCostcost_nestloop(Costoutercost,Costinnercost,intoutertuples,
3939
intinnertuples,intouterpages,boolis_indexjoin);
4040
externCostcost_mergejoin(Costoutercost,Costinnercost,

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