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Commit12c99c8

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Invent qsort_interruptible().
Justin Pryzby reported that some scenarios could cause gatheringof extended statistics to spend many seconds in an un-cancelableqsort() operation. To fix, invent qsort_interruptible(), which isjust like qsort_arg() except that it will also do CHECK_FOR_INTERRUPTSevery so often. This bloats the backend by a couple of kB, whichseems like a good investment. (We considered just enablingCHECK_FOR_INTERRUPTS in the existing qsort and qsort_arg functions,but there are some callers for which that'd demonstrably be unsafe.Opt-in seems like a better way.)For now, just apply qsort_interruptible() in statistics collection.There's probably more places where it could be useful, but we canalways change other call sites as we find problems.Back-patch to v14. Before that we didn't have extended stats onexpressions, so that the problem was less severe. Also, this patchdepends on the sort_template infrastructure introduced in v14.Tom Lane and Justin PryzbyDiscussion:https://postgr.es/m/20220509000108.GQ28830@telsasoft.com
1 parentd8759a4 commit12c99c8

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10 files changed

+80
-55
lines changed

10 files changed

+80
-55
lines changed

‎src/backend/commands/analyze.c‎

Lines changed: 13 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -100,7 +100,7 @@ static VacAttrStats *examine_attribute(Relation onerel, int attnum,
100100
staticintacquire_sample_rows(Relationonerel,intelevel,
101101
HeapTuple*rows,inttargrows,
102102
double*totalrows,double*totaldeadrows);
103-
staticintcompare_rows(constvoid*a,constvoid*b);
103+
staticintcompare_rows(constvoid*a,constvoid*b,void*arg);
104104
staticintacquire_inherited_sample_rows(Relationonerel,intelevel,
105105
HeapTuple*rows,inttargrows,
106106
double*totalrows,double*totaldeadrows);
@@ -1306,7 +1306,8 @@ acquire_sample_rows(Relation onerel, int elevel,
13061306
* tuples are already sorted.
13071307
*/
13081308
if (numrows==targrows)
1309-
qsort((void*)rows,numrows,sizeof(HeapTuple),compare_rows);
1309+
qsort_interruptible((void*)rows,numrows,sizeof(HeapTuple),
1310+
compare_rows,NULL);
13101311

13111312
/*
13121313
* Estimate total numbers of live and dead rows in relation, extrapolating
@@ -1342,10 +1343,10 @@ acquire_sample_rows(Relation onerel, int elevel,
13421343
}
13431344

13441345
/*
1345-
*qsort comparator for sorting rows[] array
1346+
*Comparator for sorting rows[] array
13461347
*/
13471348
staticint
1348-
compare_rows(constvoid*a,constvoid*b)
1349+
compare_rows(constvoid*a,constvoid*b,void*arg)
13491350
{
13501351
HeapTupleha=*(constHeapTuple*)a;
13511352
HeapTuplehb=*(constHeapTuple*)b;
@@ -1839,7 +1840,7 @@ static void compute_scalar_stats(VacAttrStatsP stats,
18391840
intsamplerows,
18401841
doubletotalrows);
18411842
staticintcompare_scalars(constvoid*a,constvoid*b,void*arg);
1842-
staticintcompare_mcvs(constvoid*a,constvoid*b);
1843+
staticintcompare_mcvs(constvoid*a,constvoid*b,void*arg);
18431844
staticintanalyze_mcv_list(int*mcv_counts,
18441845
intnum_mcv,
18451846
doublestadistinct,
@@ -2476,8 +2477,8 @@ compute_scalar_stats(VacAttrStatsP stats,
24762477
/* Sort the collected values */
24772478
cxt.ssup=&ssup;
24782479
cxt.tupnoLink=tupnoLink;
2479-
qsort_arg((void*)values,values_cnt,sizeof(ScalarItem),
2480-
compare_scalars, (void*)&cxt);
2480+
qsort_interruptible((void*)values,values_cnt,sizeof(ScalarItem),
2481+
compare_scalars, (void*)&cxt);
24812482

24822483
/*
24832484
* Now scan the values in order, find the most common ones, and also
@@ -2721,8 +2722,8 @@ compute_scalar_stats(VacAttrStatsP stats,
27212722
deltafrac;
27222723

27232724
/* Sort the MCV items into position order to speed next loop */
2724-
qsort((void*)track,num_mcv,
2725-
sizeof(ScalarMCVItem),compare_mcvs);
2725+
qsort_interruptible((void*)track,num_mcv,sizeof(ScalarMCVItem),
2726+
compare_mcvs,NULL);
27262727

27272728
/*
27282729
* Collapse out the MCV items from the values[] array.
@@ -2885,7 +2886,7 @@ compute_scalar_stats(VacAttrStatsP stats,
28852886
}
28862887

28872888
/*
2888-
*qsort_arg comparator for sorting ScalarItems
2889+
*Comparator for sorting ScalarItems
28892890
*
28902891
* Aside from sorting the items, we update the tupnoLink[] array
28912892
* whenever two ScalarItems are found to contain equal datums. The array
@@ -2922,10 +2923,10 @@ compare_scalars(const void *a, const void *b, void *arg)
29222923
}
29232924

29242925
/*
2925-
*qsort comparator for sorting ScalarMCVItems by position
2926+
*Comparator for sorting ScalarMCVItems by position
29262927
*/
29272928
staticint
2928-
compare_mcvs(constvoid*a,constvoid*b)
2929+
compare_mcvs(constvoid*a,constvoid*b,void*arg)
29292930
{
29302931
intda= ((constScalarMCVItem*)a)->first;
29312932
intdb= ((constScalarMCVItem*)b)->first;

‎src/backend/statistics/extended_stats.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1129,8 +1129,8 @@ build_sorted_items(StatsBuildData *data, int *nitems,
11291129
}
11301130

11311131
/* do the sort, using the multi-sort */
1132-
qsort_arg((void*)items,nrows,sizeof(SortItem),
1133-
multi_sort_compare,mss);
1132+
qsort_interruptible((void*)items,nrows,sizeof(SortItem),
1133+
multi_sort_compare,mss);
11341134

11351135
returnitems;
11361136
}

‎src/backend/statistics/mcv.c‎

Lines changed: 7 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -404,7 +404,7 @@ count_distinct_groups(int numrows, SortItem *items, MultiSortSupport mss)
404404
*order.
405405
*/
406406
staticint
407-
compare_sort_item_count(constvoid*a,constvoid*b)
407+
compare_sort_item_count(constvoid*a,constvoid*b,void*arg)
408408
{
409409
SortItem*ia= (SortItem*)a;
410410
SortItem*ib= (SortItem*)b;
@@ -457,8 +457,8 @@ build_distinct_groups(int numrows, SortItem *items, MultiSortSupport mss,
457457
Assert(j+1==ngroups);
458458

459459
/* Sort the distinct groups by frequency (in descending order). */
460-
pg_qsort((void*)groups,ngroups,sizeof(SortItem),
461-
compare_sort_item_count);
460+
qsort_interruptible((void*)groups,ngroups,sizeof(SortItem),
461+
compare_sort_item_count,NULL);
462462

463463
*ndistinct=ngroups;
464464
returngroups;
@@ -528,8 +528,8 @@ build_column_frequencies(SortItem *groups, int ngroups,
528528
}
529529

530530
/* sort the values, deduplicate */
531-
qsort_arg((void*)result[dim],ngroups,sizeof(SortItem),
532-
sort_item_compare,ssup);
531+
qsort_interruptible((void*)result[dim],ngroups,sizeof(SortItem),
532+
sort_item_compare,ssup);
533533

534534
/*
535535
* Identify distinct values, compute frequency (there might be
@@ -696,8 +696,8 @@ statext_mcv_serialize(MCVList *mcvlist, VacAttrStats **stats)
696696

697697
PrepareSortSupportFromOrderingOp(typentry->lt_opr,&ssup[dim]);
698698

699-
qsort_arg(values[dim],counts[dim],sizeof(Datum),
700-
compare_scalars_simple,&ssup[dim]);
699+
qsort_interruptible(values[dim],counts[dim],sizeof(Datum),
700+
compare_scalars_simple,&ssup[dim]);
701701

702702
/*
703703
* Walk through the array and eliminate duplicate values, but keep the

‎src/backend/statistics/mvdistinct.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -489,8 +489,8 @@ ndistinct_for_combination(double totalrows, StatsBuildData *data,
489489
}
490490

491491
/* We can sort the array now ... */
492-
qsort_arg((void*)items,numrows,sizeof(SortItem),
493-
multi_sort_compare,mss);
492+
qsort_interruptible((void*)items,numrows,sizeof(SortItem),
493+
multi_sort_compare,mss);
494494

495495
/* ... and count the number of distinct combinations */
496496

‎src/backend/tsearch/ts_typanalyze.c‎

Lines changed: 12 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -44,8 +44,10 @@ static void prune_lexemes_hashtable(HTAB *lexemes_tab, int b_current);
4444
staticuint32lexeme_hash(constvoid*key,Sizekeysize);
4545
staticintlexeme_match(constvoid*key1,constvoid*key2,Sizekeysize);
4646
staticintlexeme_compare(constvoid*key1,constvoid*key2);
47-
staticinttrackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2);
48-
staticinttrackitem_compare_lexemes(constvoid*e1,constvoid*e2);
47+
staticinttrackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2,
48+
void*arg);
49+
staticinttrackitem_compare_lexemes(constvoid*e1,constvoid*e2,
50+
void*arg);
4951

5052

5153
/*
@@ -347,8 +349,8 @@ compute_tsvector_stats(VacAttrStats *stats,
347349
*/
348350
if (num_mcelem<track_len)
349351
{
350-
qsort(sort_table,track_len,sizeof(TrackItem*),
351-
trackitem_compare_frequencies_desc);
352+
qsort_interruptible(sort_table,track_len,sizeof(TrackItem*),
353+
trackitem_compare_frequencies_desc,NULL);
352354
/* reset minfreq to the smallest frequency we're keeping */
353355
minfreq=sort_table[num_mcelem-1]->frequency;
354356
}
@@ -376,8 +378,8 @@ compute_tsvector_stats(VacAttrStats *stats,
376378
* presorted we can employ binary search for that. See
377379
* ts_selfuncs.c for a real usage scenario.
378380
*/
379-
qsort(sort_table,num_mcelem,sizeof(TrackItem*),
380-
trackitem_compare_lexemes);
381+
qsort_interruptible(sort_table,num_mcelem,sizeof(TrackItem*),
382+
trackitem_compare_lexemes,NULL);
381383

382384
/* Must copy the target values into anl_context */
383385
old_context=MemoryContextSwitchTo(stats->anl_context);
@@ -510,10 +512,10 @@ lexeme_compare(const void *key1, const void *key2)
510512
}
511513

512514
/*
513-
*qsort() comparator for sorting TrackItems on frequencies (descending sort)
515+
*Comparator for sorting TrackItems on frequencies (descending sort)
514516
*/
515517
staticint
516-
trackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2)
518+
trackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2,void*arg)
517519
{
518520
constTrackItem*const*t1= (constTrackItem*const*)e1;
519521
constTrackItem*const*t2= (constTrackItem*const*)e2;
@@ -522,10 +524,10 @@ trackitem_compare_frequencies_desc(const void *e1, const void *e2)
522524
}
523525

524526
/*
525-
*qsort() comparator for sorting TrackItems on lexemes
527+
*Comparator for sorting TrackItems on lexemes
526528
*/
527529
staticint
528-
trackitem_compare_lexemes(constvoid*e1,constvoid*e2)
530+
trackitem_compare_lexemes(constvoid*e1,constvoid*e2,void*arg)
529531
{
530532
constTrackItem*const*t1= (constTrackItem*const*)e1;
531533
constTrackItem*const*t2= (constTrackItem*const*)e2;

‎src/backend/utils/adt/array_typanalyze.c‎

Lines changed: 16 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -86,9 +86,9 @@ static void prune_element_hashtable(HTAB *elements_tab, int b_current);
8686
staticuint32element_hash(constvoid*key,Sizekeysize);
8787
staticintelement_match(constvoid*key1,constvoid*key2,Sizekeysize);
8888
staticintelement_compare(constvoid*key1,constvoid*key2);
89-
staticinttrackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2);
90-
staticinttrackitem_compare_element(constvoid*e1,constvoid*e2);
91-
staticintcountitem_compare_count(constvoid*e1,constvoid*e2);
89+
staticinttrackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2,void*arg);
90+
staticinttrackitem_compare_element(constvoid*e1,constvoid*e2,void*arg);
91+
staticintcountitem_compare_count(constvoid*e1,constvoid*e2,void*arg);
9292

9393

9494
/*
@@ -502,8 +502,8 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
502502
*/
503503
if (num_mcelem<track_len)
504504
{
505-
qsort(sort_table,track_len,sizeof(TrackItem*),
506-
trackitem_compare_frequencies_desc);
505+
qsort_interruptible(sort_table,track_len,sizeof(TrackItem*),
506+
trackitem_compare_frequencies_desc,NULL);
507507
/* reset minfreq to the smallest frequency we're keeping */
508508
minfreq=sort_table[num_mcelem-1]->frequency;
509509
}
@@ -522,8 +522,8 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
522522
* the element type's default comparison function. This permits
523523
* fast binary searches in selectivity estimation functions.
524524
*/
525-
qsort(sort_table,num_mcelem,sizeof(TrackItem*),
526-
trackitem_compare_element);
525+
qsort_interruptible(sort_table,num_mcelem,sizeof(TrackItem*),
526+
trackitem_compare_element,NULL);
527527

528528
/* Must copy the target values into anl_context */
529529
old_context=MemoryContextSwitchTo(stats->anl_context);
@@ -599,8 +599,9 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
599599
{
600600
sorted_count_items[j++]=count_item;
601601
}
602-
qsort(sorted_count_items,count_items_count,
603-
sizeof(DECountItem*),countitem_compare_count);
602+
qsort_interruptible(sorted_count_items,count_items_count,
603+
sizeof(DECountItem*),
604+
countitem_compare_count,NULL);
604605

605606
/*
606607
* Prepare to fill stanumbers with the histogram, followed by the
@@ -751,10 +752,10 @@ element_compare(const void *key1, const void *key2)
751752
}
752753

753754
/*
754-
*qsort() comparator for sorting TrackItems by frequencies (descending sort)
755+
*Comparator for sorting TrackItems by frequencies (descending sort)
755756
*/
756757
staticint
757-
trackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2)
758+
trackitem_compare_frequencies_desc(constvoid*e1,constvoid*e2,void*arg)
758759
{
759760
constTrackItem*const*t1= (constTrackItem*const*)e1;
760761
constTrackItem*const*t2= (constTrackItem*const*)e2;
@@ -763,10 +764,10 @@ trackitem_compare_frequencies_desc(const void *e1, const void *e2)
763764
}
764765

765766
/*
766-
*qsort() comparator for sorting TrackItems by element values
767+
*Comparator for sorting TrackItems by element values
767768
*/
768769
staticint
769-
trackitem_compare_element(constvoid*e1,constvoid*e2)
770+
trackitem_compare_element(constvoid*e1,constvoid*e2,void*arg)
770771
{
771772
constTrackItem*const*t1= (constTrackItem*const*)e1;
772773
constTrackItem*const*t2= (constTrackItem*const*)e2;
@@ -775,10 +776,10 @@ trackitem_compare_element(const void *e1, const void *e2)
775776
}
776777

777778
/*
778-
*qsort() comparator for sorting DECountItems by count
779+
*Comparator for sorting DECountItems by count
779780
*/
780781
staticint
781-
countitem_compare_count(constvoid*e1,constvoid*e2)
782+
countitem_compare_count(constvoid*e1,constvoid*e2,void*arg)
782783
{
783784
constDECountItem*const*t1= (constDECountItem*const*)e1;
784785
constDECountItem*const*t2= (constDECountItem*const*)e2;

‎src/backend/utils/adt/rangetypes_typanalyze.c‎

Lines changed: 8 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -32,7 +32,7 @@
3232
#include"utils/rangetypes.h"
3333
#include"utils/multirangetypes.h"
3434

35-
staticintfloat8_qsort_cmp(constvoid*a1,constvoid*a2);
35+
staticintfloat8_qsort_cmp(constvoid*a1,constvoid*a2,void*arg);
3636
staticintrange_bound_qsort_cmp(constvoid*a1,constvoid*a2,void*arg);
3737
staticvoidcompute_range_stats(VacAttrStats*stats,
3838
AnalyzeAttrFetchFuncfetchfunc,intsamplerows,
@@ -93,7 +93,7 @@ multirange_typanalyze(PG_FUNCTION_ARGS)
9393
* Comparison function for sorting float8s, used for range lengths.
9494
*/
9595
staticint
96-
float8_qsort_cmp(constvoid*a1,constvoid*a2)
96+
float8_qsort_cmp(constvoid*a1,constvoid*a2,void*arg)
9797
{
9898
constfloat8*f1= (constfloat8*)a1;
9999
constfloat8*f2= (constfloat8*)a2;
@@ -280,10 +280,10 @@ compute_range_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
280280
if (non_empty_cnt >=2)
281281
{
282282
/* Sort bound values */
283-
qsort_arg(lowers,non_empty_cnt,sizeof(RangeBound),
284-
range_bound_qsort_cmp,typcache);
285-
qsort_arg(uppers,non_empty_cnt,sizeof(RangeBound),
286-
range_bound_qsort_cmp,typcache);
283+
qsort_interruptible(lowers,non_empty_cnt,sizeof(RangeBound),
284+
range_bound_qsort_cmp,typcache);
285+
qsort_interruptible(uppers,non_empty_cnt,sizeof(RangeBound),
286+
range_bound_qsort_cmp,typcache);
287287

288288
num_hist=non_empty_cnt;
289289
if (num_hist>num_bins)
@@ -345,7 +345,8 @@ compute_range_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
345345
* Ascending sort of range lengths for further filling of
346346
* histogram
347347
*/
348-
qsort(lengths,non_empty_cnt,sizeof(float8),float8_qsort_cmp);
348+
qsort_interruptible(lengths,non_empty_cnt,sizeof(float8),
349+
float8_qsort_cmp,NULL);
349350

350351
num_hist=non_empty_cnt;
351352
if (num_hist>num_bins)

‎src/backend/utils/sort/Makefile‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -16,6 +16,7 @@ override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
1616

1717
OBJS =\
1818
logtape.o\
19+
qsort_interruptible.o\
1920
sharedtuplestore.o\
2021
sortsupport.o\
2122
tuplesort.o\
Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
1+
/*
2+
*qsort_interruptible.c: qsort_arg that includes CHECK_FOR_INTERRUPTS
3+
*/
4+
5+
#include"postgres.h"
6+
#include"miscadmin.h"
7+
8+
#defineST_SORT qsort_interruptible
9+
#defineST_ELEMENT_TYPE_VOID
10+
#defineST_COMPARATOR_TYPE_NAME qsort_arg_comparator
11+
#defineST_COMPARE_RUNTIME_POINTER
12+
#defineST_COMPARE_ARG_TYPE void
13+
#defineST_SCOPE
14+
#defineST_DEFINE
15+
#defineST_CHECK_FOR_INTERRUPTS
16+
#include"lib/sort_template.h"

‎src/include/port.h‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -499,6 +499,9 @@ typedef int (*qsort_arg_comparator) (const void *a, const void *b, void *arg);
499499
externvoidqsort_arg(void*base,size_tnel,size_telsize,
500500
qsort_arg_comparatorcmp,void*arg);
501501

502+
externvoidqsort_interruptible(void*base,size_tnel,size_telsize,
503+
qsort_arg_comparatorcmp,void*arg);
504+
502505
externvoid*bsearch_arg(constvoid*key,constvoid*base,
503506
size_tnmemb,size_tsize,
504507
int (*compar) (constvoid*,constvoid*,void*),

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