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Tweak dynahash.c to not allocate so many entries at once when dealing
with a table that has a small predicted size. Avoids wasting several hundred K on the timezone hash table, which is likely to have only one or a few entries, but the entries use up 10Kb apiece ...
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@ -9,7 +9,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.62 2005/06/18 20:51:30 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.63 2005/06/26 23:32:33 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -311,6 +311,7 @@ init_htab(HTAB *hashp, long nelem)
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{
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HASHHDR *hctl = hashp->hctl;
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HASHSEGMENT *segp;
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long lnbuckets;
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int nbuckets;
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int nsegs;
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@ -319,9 +320,9 @@ init_htab(HTAB *hashp, long nelem)
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* number of buckets. Allocate space for the next greater power of
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* two number of buckets
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*/
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nelem = (nelem - 1) / hctl->ffactor + 1;
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lnbuckets = (nelem - 1) / hctl->ffactor + 1;
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nbuckets = 1 << my_log2(nelem);
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nbuckets = 1 << my_log2(lnbuckets);
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hctl->max_bucket = hctl->low_mask = nbuckets - 1;
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hctl->high_mask = (nbuckets << 1) - 1;
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@ -363,6 +364,10 @@ init_htab(HTAB *hashp, long nelem)
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return false;
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}
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/* Choose number of entries to allocate at a time */
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hctl->nelem_alloc = (int) Min(nelem, HASHELEMENT_ALLOC_MAX);
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hctl->nelem_alloc = Max(hctl->nelem_alloc, 1);
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#if HASH_DEBUG
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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",
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"TABLE POINTER ", hashp,
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@ -394,7 +399,8 @@ hash_estimate_size(long num_entries, Size entrysize)
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nSegments,
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nDirEntries,
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nElementAllocs,
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elementSize;
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elementSize,
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elementAllocCnt;
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/* estimate number of buckets wanted */
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nBuckets = 1L << my_log2((num_entries - 1) / DEF_FFACTOR + 1);
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@ -411,10 +417,12 @@ hash_estimate_size(long num_entries, Size entrysize)
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size += MAXALIGN(nDirEntries * sizeof(HASHSEGMENT));
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/* segments */
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size += nSegments * MAXALIGN(DEF_SEGSIZE * sizeof(HASHBUCKET));
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/* elements --- allocated in groups of HASHELEMENT_ALLOC_INCR */
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/* elements --- allocated in groups of up to HASHELEMENT_ALLOC_MAX */
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elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
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nElementAllocs = (num_entries - 1) / HASHELEMENT_ALLOC_INCR + 1;
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size += nElementAllocs * HASHELEMENT_ALLOC_INCR * elementSize;
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elementAllocCnt = Min(num_entries, HASHELEMENT_ALLOC_MAX);
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elementAllocCnt = Max(elementAllocCnt, 1);
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nElementAllocs = (num_entries - 1) / elementAllocCnt + 1;
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size += nElementAllocs * elementAllocCnt * elementSize;
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return size;
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}
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@ -633,7 +641,7 @@ hash_search(HTAB *hashp,
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if (currBucket == NULL)
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{
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/* no free elements. allocate another chunk of buckets */
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if (!element_alloc(hashp, HASHELEMENT_ALLOC_INCR))
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if (!element_alloc(hashp, hctl->nelem_alloc))
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{
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/* out of memory */
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if (action == HASH_ENTER_NULL)
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.38 2005/06/18 20:51:30 tgl Exp $
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* $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.39 2005/06/26 23:32:34 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -97,6 +97,7 @@ typedef struct HASHHDR
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Size entrysize; /* total user element size in bytes */
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long max_dsize; /* 'dsize' limit if directory is fixed
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* size */
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int nelem_alloc; /* number of entries to allocate at once */
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HASHELEMENT *freeList; /* linked list of free elements */
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#ifdef HASH_STATISTICS
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long accesses;
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@ -158,8 +159,8 @@ typedef struct HASHCTL
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/* max_dsize value to indicate expansible directory */
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#define NO_MAX_DSIZE (-1)
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/* number of hash elements allocated at once */
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#define HASHELEMENT_ALLOC_INCR (32)
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/* max number of hash elements allocated at once */
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#define HASHELEMENT_ALLOC_MAX (32)
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/* hash_search operations */
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typedef enum
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@ -6,7 +6,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.35 2005/06/20 08:00:51 neilc Exp $
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* $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.36 2005/06/26 23:32:34 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -978,7 +978,7 @@ init_timezone_hashtable(void)
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hash_ctl.entrysize = sizeof(pg_tz);
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timezone_cache = hash_create("Timezones",
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31,
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4,
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&hash_ctl,
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HASH_ELEM);
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if (!timezone_cache)
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