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Shared-memory hashtables have non-extensible directories, which means

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it's a good idea to choose the directory size based on the expected
number of entries.  But ShmemInitHash was using a hard-wired constant.
Boo hiss.  This accounts for recent report of postmaster failure when
asking for 64K or more buffers.
This commit is contained in:
Tom Lane
2000-02-26 05:25:55 +00:00
parent c05abfb1a8
commit 08b1040374
3 changed files with 53 additions and 25 deletions
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35
src/backend/utils/hash/dynahash.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/hash/dynahash.c,v 1.28 2000/01/26 05:57:24 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/hash/dynahash.c,v 1.29 2000/02/26 05:25:54 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -328,10 +328,7 @@ init_htab(HTAB *hashp, int nelem)
{
*segp = seg_alloc(hashp);
if (*segp == (SEG_OFFSET) 0)
{
hash_destroy(hashp);
return 0;
}
return -1;
}
#if HASH_DEBUG
@@ -392,6 +389,34 @@ hash_estimate_size(long num_entries, long keysize, long datasize)
return size;
}
/*
* Select an appropriate directory size for a hashtable with the given
* maximum number of entries.
* This is only needed for hashtables in shared memory, whose directories
* cannot be expanded dynamically.
* NB: assumes that all hash structure parameters have default values!
*
* XXX this had better agree with the behavior of init_htab()...
*/
long
hash_select_dirsize(long num_entries)
{
long nBuckets,
nSegments,
nDirEntries;
/* estimate number of buckets wanted */
nBuckets = 1L << my_log2((num_entries - 1) / DEF_FFACTOR + 1);
/* # of segments needed for nBuckets */
nSegments = 1L << my_log2((nBuckets - 1) / DEF_SEGSIZE + 1);
/* directory entries */
nDirEntries = DEF_DIRSIZE;
while (nDirEntries < nSegments)
nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
return nDirEntries;
}
/********************** DESTROY ROUTINES ************************/