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Commit02a2e8b

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Modify additional power 2 calculations to use new helper functions
2nd pass of modifying various places which obtain the next powerof 2 of a number and make them use the new functions added inf0705bb.In passing, also modify num_combinations(). This can be implementedusing simple bitshifting rather than looping.Reviewed-by: John NaylorDiscussion:https://postgr.es/m/20200114173553.GE32763%40fetter.org
1 parentc018786 commit02a2e8b

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5 files changed

+16
-38
lines changed

5 files changed

+16
-38
lines changed

‎src/backend/access/gin/ginfast.c‎

Lines changed: 3 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -25,6 +25,7 @@
2525
#include"catalog/pg_am.h"
2626
#include"commands/vacuum.h"
2727
#include"miscadmin.h"
28+
#include"port/pg_bitutils.h"
2829
#include"postmaster/autovacuum.h"
2930
#include"storage/indexfsm.h"
3031
#include"storage/lmgr.h"
@@ -503,10 +504,7 @@ ginHeapTupleFastCollect(GinState *ginstate,
503504
* initially. Make it a power of 2 to avoid wasting memory when
504505
* resizing (since palloc likes powers of 2).
505506
*/
506-
collector->lentuples=16;
507-
while (collector->lentuples<nentries)
508-
collector->lentuples *=2;
509-
507+
collector->lentuples=pg_nextpower2_32(Max(16,nentries));
510508
collector->tuples= (IndexTuple*)palloc(sizeof(IndexTuple)*collector->lentuples);
511509
}
512510
elseif (collector->lentuples<collector->ntuples+nentries)
@@ -516,11 +514,7 @@ ginHeapTupleFastCollect(GinState *ginstate,
516514
* overflow, though we could get to a value that exceeds
517515
* MaxAllocSize/sizeof(IndexTuple), causing an error in repalloc.
518516
*/
519-
do
520-
{
521-
collector->lentuples *=2;
522-
}while (collector->lentuples<collector->ntuples+nentries);
523-
517+
collector->lentuples=pg_nextpower2_32(collector->ntuples+nentries);
524518
collector->tuples= (IndexTuple*)repalloc(collector->tuples,
525519
sizeof(IndexTuple)*collector->lentuples);
526520
}

‎src/backend/executor/nodeHash.c‎

Lines changed: 2 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -831,9 +831,7 @@ ExecChooseHashTableSize(double ntuples, int tupwidth, bool useskew,
831831
dbatch=ceil(inner_rel_bytes / (hash_table_bytes-bucket_bytes));
832832
dbatch=Min(dbatch,max_pointers);
833833
minbatch= (int)dbatch;
834-
nbatch=2;
835-
while (nbatch<minbatch)
836-
nbatch <<=1;
834+
nbatch=pg_nextpower2_32(Max(2,minbatch));
837835
}
838836

839837
Assert(nbuckets>0);
@@ -2272,9 +2270,7 @@ ExecHashBuildSkewHash(HashJoinTable hashtable, Hash *node, int mcvsToUse)
22722270
* MaxAllocSize/sizeof(void *)/8, but that is not currently possible
22732271
* since we limit pg_statistic entries to much less than that.
22742272
*/
2275-
nbuckets=2;
2276-
while (nbuckets <=mcvsToUse)
2277-
nbuckets <<=1;
2273+
nbuckets=pg_nextpower2_32(mcvsToUse+1);
22782274
/* use two more bits just to help avoid collisions */
22792275
nbuckets <<=2;
22802276

‎src/backend/nodes/list.c‎

Lines changed: 7 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@
1818
#include"postgres.h"
1919

2020
#include"nodes/pg_list.h"
21+
#include"port/pg_bitutils.h"
2122
#include"utils/memdebug.h"
2223
#include"utils/memutils.h"
2324

@@ -119,9 +120,7 @@ new_list(NodeTag type, int min_size)
119120
* that's more than twice the size of an existing list, so the size limits
120121
* within palloc will ensure that we don't overflow here.
121122
*/
122-
max_size=8;/* semi-arbitrary small power of 2 */
123-
while (max_size<min_size+LIST_HEADER_OVERHEAD)
124-
max_size *=2;
123+
max_size=pg_nextpower2_32(Max(8,min_size+LIST_HEADER_OVERHEAD));
125124
max_size-=LIST_HEADER_OVERHEAD;
126125
#else
127126

@@ -160,12 +159,12 @@ enlarge_list(List *list, int min_size)
160159

161160
/*
162161
* As above, we prefer power-of-two total allocations; but here we need
163-
* not account for list header overhead. The existing max length might
164-
* not be a power of 2, so don't rely on that.
162+
* not account for list header overhead.
165163
*/
166-
new_max_len=16;/* semi-arbitrary small power of 2 */
167-
while (new_max_len<min_size)
168-
new_max_len *=2;
164+
165+
/* clamp the minimum value to 16, a semi-arbitrary small power of 2 */
166+
new_max_len=pg_nextpower2_32(Max(16,min_size));
167+
169168
#else
170169
/* As above, don't allocate anything extra */
171170
new_max_len=min_size;

‎src/backend/statistics/mvdistinct.c‎

Lines changed: 1 addition & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -576,15 +576,7 @@ n_choose_k(int n, int k)
576576
staticint
577577
num_combinations(intn)
578578
{
579-
intk;
580-
intncombs=1;
581-
582-
for (k=1;k <=n;k++)
583-
ncombs *=2;
584-
585-
ncombs-= (n+1);
586-
587-
returnncombs;
579+
return (1 <<n)- (n+1);
588580
}
589581

590582
/*

‎src/backend/utils/adt/arrayfuncs.c‎

Lines changed: 3 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -24,6 +24,7 @@
2424
#include"nodes/nodeFuncs.h"
2525
#include"nodes/supportnodes.h"
2626
#include"optimizer/optimizer.h"
27+
#include"port/pg_bitutils.h"
2728
#include"utils/array.h"
2829
#include"utils/arrayaccess.h"
2930
#include"utils/builtins.h"
@@ -5313,9 +5314,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
53135314
memcpy(&astate->lbs[1],lbs,ndims*sizeof(int));
53145315

53155316
/* Allocate at least enough data space for this item */
5316-
astate->abytes=1024;
5317-
while (astate->abytes <=ndatabytes)
5318-
astate->abytes *=2;
5317+
astate->abytes=pg_nextpower2_32(Max(1024,ndatabytes+1));
53195318
astate->data= (char*)palloc(astate->abytes);
53205319
}
53215320
else
@@ -5362,9 +5361,7 @@ accumArrayResultArr(ArrayBuildStateArr *astate,
53625361
* First input with nulls; we must retrospectively handle any
53635362
* previous inputs by marking all their items non-null.
53645363
*/
5365-
astate->aitems=256;
5366-
while (astate->aitems <=newnitems)
5367-
astate->aitems *=2;
5364+
astate->aitems=pg_nextpower2_32(Max(256,newnitems+1));
53685365
astate->nullbitmap= (bits8*)palloc((astate->aitems+7) /8);
53695366
array_bitmap_copy(astate->nullbitmap,0,
53705367
NULL,0,

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