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Commit06ae88a

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committed
Tweak dynahash.c to not allocate so many entries at once when dealing
with a table that has a small predicted size. Avoids wasting severalhundred K on the timezone hash table, which is likely to have only oneor a few entries, but the entries use up 10Kb apiece ...
1 parent943b396 commit06ae88a

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3 files changed

+22
-13
lines changed

3 files changed

+22
-13
lines changed

‎src/backend/utils/hash/dynahash.c‎

Lines changed: 16 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.62 2005/06/18 20:51:30 tgl Exp $
12+
* $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.63 2005/06/26 23:32:33 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -311,6 +311,7 @@ init_htab(HTAB *hashp, long nelem)
311311
{
312312
HASHHDR*hctl=hashp->hctl;
313313
HASHSEGMENT*segp;
314+
longlnbuckets;
314315
intnbuckets;
315316
intnsegs;
316317

@@ -319,9 +320,9 @@ init_htab(HTAB *hashp, long nelem)
319320
* number of buckets. Allocate space for the next greater power of
320321
* two number of buckets
321322
*/
322-
nelem= (nelem-1) /hctl->ffactor+1;
323+
lnbuckets= (nelem-1) /hctl->ffactor+1;
323324

324-
nbuckets=1 <<my_log2(nelem);
325+
nbuckets=1 <<my_log2(lnbuckets);
325326

326327
hctl->max_bucket=hctl->low_mask=nbuckets-1;
327328
hctl->high_mask= (nbuckets <<1)-1;
@@ -363,6 +364,10 @@ init_htab(HTAB *hashp, long nelem)
363364
return false;
364365
}
365366

367+
/* Choose number of entries to allocate at a time */
368+
hctl->nelem_alloc= (int)Min(nelem,HASHELEMENT_ALLOC_MAX);
369+
hctl->nelem_alloc=Max(hctl->nelem_alloc,1);
370+
366371
#ifHASH_DEBUG
367372
fprintf(stderr,"init_htab:\n%s%p\n%s%ld\n%s%ld\n%s%d\n%s%ld\n%s%u\n%s%x\n%s%x\n%s%ld\n%s%ld\n",
368373
"TABLE POINTER ",hashp,
@@ -394,7 +399,8 @@ hash_estimate_size(long num_entries, Size entrysize)
394399
nSegments,
395400
nDirEntries,
396401
nElementAllocs,
397-
elementSize;
402+
elementSize,
403+
elementAllocCnt;
398404

399405
/* estimate number of buckets wanted */
400406
nBuckets=1L <<my_log2((num_entries-1) /DEF_FFACTOR+1);
@@ -411,10 +417,12 @@ hash_estimate_size(long num_entries, Size entrysize)
411417
size+=MAXALIGN(nDirEntries*sizeof(HASHSEGMENT));
412418
/* segments */
413419
size+=nSegments*MAXALIGN(DEF_SEGSIZE*sizeof(HASHBUCKET));
414-
/* elements --- allocated in groups ofHASHELEMENT_ALLOC_INCR */
420+
/* elements --- allocated in groups ofup to HASHELEMENT_ALLOC_MAX */
415421
elementSize=MAXALIGN(sizeof(HASHELEMENT))+MAXALIGN(entrysize);
416-
nElementAllocs= (num_entries-1) /HASHELEMENT_ALLOC_INCR+1;
417-
size+=nElementAllocs*HASHELEMENT_ALLOC_INCR*elementSize;
422+
elementAllocCnt=Min(num_entries,HASHELEMENT_ALLOC_MAX);
423+
elementAllocCnt=Max(elementAllocCnt,1);
424+
nElementAllocs= (num_entries-1) /elementAllocCnt+1;
425+
size+=nElementAllocs*elementAllocCnt*elementSize;
418426

419427
returnsize;
420428
}
@@ -633,7 +641,7 @@ hash_search(HTAB *hashp,
633641
if (currBucket==NULL)
634642
{
635643
/* no free elements. allocate another chunk of buckets */
636-
if (!element_alloc(hashp,HASHELEMENT_ALLOC_INCR))
644+
if (!element_alloc(hashp,hctl->nelem_alloc))
637645
{
638646
/* out of memory */
639647
if (action==HASH_ENTER_NULL)

‎src/include/utils/hsearch.h‎

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.38 2005/06/18 20:51:30 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.39 2005/06/26 23:32:34 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -97,6 +97,7 @@ typedef struct HASHHDR
9797
Sizeentrysize;/* total user element size in bytes */
9898
longmax_dsize;/* 'dsize' limit if directory is fixed
9999
* size */
100+
intnelem_alloc;/* number of entries to allocate at once */
100101
HASHELEMENT*freeList;/* linked list of free elements */
101102
#ifdefHASH_STATISTICS
102103
longaccesses;
@@ -158,8 +159,8 @@ typedef struct HASHCTL
158159

159160
/* max_dsize value to indicate expansible directory */
160161
#defineNO_MAX_DSIZE(-1)
161-
/* number of hash elements allocated at once */
162-
#defineHASHELEMENT_ALLOC_INCR(32)
162+
/*maxnumber of hash elements allocated at once */
163+
#defineHASHELEMENT_ALLOC_MAX(32)
163164

164165
/* hash_search operations */
165166
typedefenum

‎src/timezone/pgtz.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
77
*
88
* IDENTIFICATION
9-
* $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.35 2005/06/20 08:00:51 neilc Exp $
9+
* $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.36 2005/06/26 23:32:34 tgl Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -978,7 +978,7 @@ init_timezone_hashtable(void)
978978
hash_ctl.entrysize=sizeof(pg_tz);
979979

980980
timezone_cache=hash_create("Timezones",
981-
31,
981+
4,
982982
&hash_ctl,
983983
HASH_ELEM);
984984
if (!timezone_cache)

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