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Commitd025cf8

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Modify various power 2 calculations to use new helper functions
First pass of modifying various places that obtain the next power of 2 ofa number and make them use the new functions added in pg_bitutils.hinstead.This also removes the _hash_log2() function. There are no longer anycallers in core. Other users can swap their _hash_log2(n) call to make useof pg_ceil_log2_32(n).Author: David Fetter, with some minor adjustments by meReviewed-by: John Naylor, Jesse ZhangDiscussion:https://postgr.es/m/20200114173553.GE32763%40fetter.org
1 parent50a38f6 commitd025cf8

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7 files changed

+32
-62
lines changed

7 files changed

+32
-62
lines changed

‎src/backend/access/hash/hashpage.c

Lines changed: 11 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -31,6 +31,7 @@
3131
#include"access/hash.h"
3232
#include"access/hash_xlog.h"
3333
#include"miscadmin.h"
34+
#include"port/pg_bitutils.h"
3435
#include"storage/lmgr.h"
3536
#include"storage/predicate.h"
3637
#include"storage/smgr.h"
@@ -502,7 +503,7 @@ _hash_init_metabuffer(Buffer buf, double num_tuples, RegProcedure procid,
502503
doublednumbuckets;
503504
uint32num_buckets;
504505
uint32spare_index;
505-
uint32i;
506+
uint32lshift;
506507

507508
/*
508509
* Choose the number of initial bucket pages to match the fill factor
@@ -542,15 +543,12 @@ _hash_init_metabuffer(Buffer buf, double num_tuples, RegProcedure procid,
542543
metap->hashm_nmaps=0;
543544
metap->hashm_ffactor=ffactor;
544545
metap->hashm_bsize=HashGetMaxBitmapSize(page);
546+
545547
/* find largest bitmap array size that will fit in page size */
546-
for (i=_hash_log2(metap->hashm_bsize);i>0;--i)
547-
{
548-
if ((1 <<i) <=metap->hashm_bsize)
549-
break;
550-
}
551-
Assert(i>0);
552-
metap->hashm_bmsize=1 <<i;
553-
metap->hashm_bmshift=i+BYTE_TO_BIT;
548+
lshift=pg_leftmost_one_pos32(metap->hashm_bsize);
549+
Assert(lshift>0);
550+
metap->hashm_bmsize=1 <<lshift;
551+
metap->hashm_bmshift=lshift+BYTE_TO_BIT;
554552
Assert((1 <<BMPG_SHIFT(metap))== (BMPG_MASK(metap)+1));
555553

556554
/*
@@ -570,7 +568,7 @@ _hash_init_metabuffer(Buffer buf, double num_tuples, RegProcedure procid,
570568
* Set highmask as next immediate ((2 ^ x) - 1), which should be
571569
* sufficient to cover num_buckets.
572570
*/
573-
metap->hashm_highmask=(1 << (_hash_log2(num_buckets+1)))-1;
571+
metap->hashm_highmask=pg_nextpower2_32(num_buckets+1)-1;
574572
metap->hashm_lowmask= (metap->hashm_highmask >>1);
575573

576574
MemSet(metap->hashm_spares,0,sizeof(metap->hashm_spares));
@@ -659,9 +657,9 @@ _hash_expandtable(Relation rel, Buffer metabuf)
659657
*
660658
* Ideally we'd allow bucket numbers up to UINT_MAX-1 (no higher because
661659
* the calculation maxbucket+1 mustn't overflow). Currently we restrict
662-
* to half thatbecause of overflow looping in _hash_log2() and
663-
*insufficientspace in hashm_spares[]. It's moot anyway because an
664-
*index with 2^32buckets would certainly overflow BlockNumber and hence
660+
* to half thatto prevent failure of pg_ceil_log2_32() and insufficient
661+
* space in hashm_spares[]. It's moot anyway because an index with 2^32
662+
* buckets would certainly overflow BlockNumber and hence
665663
* _hash_alloc_buckets() would fail, but if we supported buckets smaller
666664
* than a disk block then this would be an independent constraint.
667665
*

‎src/backend/access/hash/hashsort.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -29,6 +29,7 @@
2929
#include"commands/progress.h"
3030
#include"miscadmin.h"
3131
#include"pgstat.h"
32+
#include"port/pg_bitutils.h"
3233
#include"utils/tuplesort.h"
3334

3435

@@ -69,7 +70,7 @@ _h_spoolinit(Relation heap, Relation index, uint32 num_buckets)
6970
* NOTE : This hash mask calculation should be in sync with similar
7071
* calculation in _hash_init_metabuffer.
7172
*/
72-
hspool->high_mask=(((uint32)1) <<_hash_log2(num_buckets+1))-1;
73+
hspool->high_mask=pg_nextpower2_32(num_buckets+1)-1;
7374
hspool->low_mask= (hspool->high_mask >>1);
7475
hspool->max_buckets=num_buckets-1;
7576

‎src/backend/access/hash/hashutil.c

Lines changed: 2 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,7 @@
1717
#include"access/hash.h"
1818
#include"access/reloptions.h"
1919
#include"access/relscan.h"
20+
#include"port/pg_bitutils.h"
2021
#include"storage/buf_internals.h"
2122
#include"utils/lsyscache.h"
2223
#include"utils/rel.h"
@@ -134,21 +135,6 @@ _hash_hashkey2bucket(uint32 hashkey, uint32 maxbucket,
134135
returnbucket;
135136
}
136137

137-
/*
138-
* _hash_log2 -- returns ceil(lg2(num))
139-
*/
140-
uint32
141-
_hash_log2(uint32num)
142-
{
143-
uint32i,
144-
limit;
145-
146-
limit=1;
147-
for (i=0;limit<num;limit <<=1,i++)
148-
;
149-
returni;
150-
}
151-
152138
/*
153139
* _hash_spareindex -- returns spare index / global splitpoint phase of the
154140
* bucket
@@ -158,8 +144,7 @@ _hash_spareindex(uint32 num_bucket)
158144
{
159145
uint32splitpoint_group;
160146
uint32splitpoint_phases;
161-
162-
splitpoint_group=_hash_log2(num_bucket);
147+
splitpoint_group=pg_ceil_log2_32(num_bucket);
163148

164149
if (splitpoint_group<HASH_SPLITPOINT_GROUPS_WITH_ONE_PHASE)
165150
returnsplitpoint_group;

‎src/backend/utils/hash/dynahash.c

Lines changed: 7 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -87,6 +87,7 @@
8787

8888
#include"access/xact.h"
8989
#include"common/hashfn.h"
90+
#include"port/pg_bitutils.h"
9091
#include"storage/shmem.h"
9192
#include"storage/spin.h"
9293
#include"utils/dynahash.h"
@@ -1718,16 +1719,15 @@ hash_corrupted(HTAB *hashp)
17181719
int
17191720
my_log2(longnum)
17201721
{
1721-
inti;
1722-
longlimit;
1723-
1724-
/* guard against too-large input, which would put us into infinite loop */
1722+
/* guard against too-large input, which would be invalid for pg_ceil_log2_*() */
17251723
if (num>LONG_MAX /2)
17261724
num=LONG_MAX /2;
17271725

1728-
for (i=0,limit=1;limit<num;i++,limit <<=1)
1729-
;
1730-
returni;
1726+
#ifSIZEOF_LONG<8
1727+
returnpg_ceil_log2_32(num);
1728+
#else
1729+
returnpg_ceil_log2_64(num);
1730+
#endif
17311731
}
17321732

17331733
/* calculate first power of 2 >= num, bounded to what will fit in a long */

‎src/include/access/hash.h

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -451,7 +451,6 @@ extern uint32 _hash_datum2hashkey(Relation rel, Datum key);
451451
externuint32_hash_datum2hashkey_type(Relationrel,Datumkey,Oidkeytype);
452452
externBucket_hash_hashkey2bucket(uint32hashkey,uint32maxbucket,
453453
uint32highmask,uint32lowmask);
454-
externuint32_hash_log2(uint32num);
455454
externuint32_hash_spareindex(uint32num_bucket);
456455
externuint32_hash_get_totalbuckets(uint32splitpoint_phase);
457456
externvoid_hash_checkpage(Relationrel,Bufferbuf,intflags);

‎src/include/lib/simplehash.h

Lines changed: 4 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,8 @@
5757
* backwards, unless they're empty or already at their optimal position.
5858
*/
5959

60+
#include"port/pg_bitutils.h"
61+
6062
/* helpers */
6163
#defineSH_MAKE_PREFIX(a) CppConcat(a,_)
6264
#defineSH_MAKE_NAME(name) SH_MAKE_NAME_(SH_MAKE_PREFIX(SH_PREFIX),name)
@@ -215,27 +217,6 @@ SH_SCOPE void SH_STAT(SH_TYPE * tb);
215217
#ifndefSIMPLEHASH_H
216218
#defineSIMPLEHASH_H
217219

218-
/* FIXME: can we move these to a central location? */
219-
220-
/* calculate ceil(log base 2) of num */
221-
staticinlineuint64
222-
sh_log2(uint64num)
223-
{
224-
inti;
225-
uint64limit;
226-
227-
for (i=0,limit=1;limit<num;i++,limit <<=1)
228-
;
229-
returni;
230-
}
231-
232-
/* calculate first power of 2 >= num */
233-
staticinlineuint64
234-
sh_pow2(uint64num)
235-
{
236-
return ((uint64)1) <<sh_log2(num);
237-
}
238-
239220
#ifdefFRONTEND
240221
#definesh_error(...) pg_log_error(__VA_ARGS__)
241222
#definesh_log(...) pg_log_info(__VA_ARGS__)
@@ -259,7 +240,7 @@ SH_COMPUTE_PARAMETERS(SH_TYPE * tb, uint32 newsize)
259240
size=Max(newsize,2);
260241

261242
/* round up size to the next power of 2, that's how bucketing works */
262-
size=sh_pow2(size);
243+
size=pg_nextpower2_64(size);
263244
Assert(size <=SH_MAX_SIZE);
264245

265246
/*
@@ -434,7 +415,7 @@ SH_GROW(SH_TYPE * tb, uint32 newsize)
434415
uint32startelem=0;
435416
uint32copyelem;
436417

437-
Assert(oldsize==sh_pow2(oldsize));
418+
Assert(oldsize==pg_nextpower2_64(oldsize));
438419
Assert(oldsize!=SH_MAX_SIZE);
439420
Assert(oldsize<newsize);
440421

‎src/include/port/pg_bitutils.h

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -13,9 +13,15 @@
1313
#ifndefPG_BITUTILS_H
1414
#definePG_BITUTILS_H
1515

16+
#ifndefFRONTEND
1617
externPGDLLIMPORTconstuint8pg_leftmost_one_pos[256];
1718
externPGDLLIMPORTconstuint8pg_rightmost_one_pos[256];
1819
externPGDLLIMPORTconstuint8pg_number_of_ones[256];
20+
#else
21+
externconstuint8pg_leftmost_one_pos[256];
22+
externconstuint8pg_rightmost_one_pos[256];
23+
externconstuint8pg_number_of_ones[256];
24+
#endif
1925

2026
/*
2127
* pg_leftmost_one_pos32

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