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Postgres FD Implementation
Commit 08b10403 authored by Tom Lane's avatar Tom Lane
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Shared-memory hashtables have non-extensible directories, which means 

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.
parent c05abfb1
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Showing with 53 additions and 25 deletions
src/backend/storage/ipc/shmem.c
View file @ 08b10403
......@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.48 2000/01/26 05:56:58 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.49 2000/02/26 05:25:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -332,7 +332,7 @@ ShmemIsValid(unsigned long addr)
HTAB *
ShmemInitHash(char *name, /* table string name for shmem index */
long init_size, /* initial table size */
long max_size, /* max size of the table (NOT USED) */
long max_size, /* max size of the table */
HASHCTL *infoP, /* info about key and bucket size */
int hash_flags) /* info about infoP */
{
......@@ -340,19 +340,21 @@ ShmemInitHash(char *name, /* table string name for shmem index */
long *location;
/*
* Hash tables allocated in shared memory have a fixed directory; it
* can't grow or other backends wouldn't be able to find it. The
* segbase is for calculating pointer values. The shared memory
* Hash tables allocated in shared memory have a fixed directory;
* it can't grow or other backends wouldn't be able to find it.
* So, make sure we make it big enough to start with.
*
* The segbase is for calculating pointer values. The shared memory
* allocator must be specified too.
*/
infoP->dsize = infoP->max_dsize = DEF_DIRSIZE;
infoP->dsize = infoP->max_dsize = hash_select_dirsize(max_size);
infoP->segbase = (long *) ShmemBase;
infoP->alloc = ShmemAlloc;
hash_flags |= HASH_SHARED_MEM | HASH_DIRSIZE;
/* look it up in the shmem index */
location = ShmemInitStruct(name,
sizeof(HHDR) + DEF_DIRSIZE * sizeof(SEG_OFFSET),
sizeof(HHDR) + infoP->dsize * sizeof(SEG_OFFSET),
&found);
/*
......
src/backend/utils/hash/dynahash.c
View file @ 08b10403
......@@ -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 ************************/
......
src/include/utils/hsearch.h
View file @ 08b10403
/*-------------------------------------------------------------------------
*
* hsearch.h
* for hashing in the new buffer manager
* for hash tables, particularly hash tables in shared memory
*
*
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: hsearch.h,v 1.13 2000/01/26 05:58:38 momjian Exp $
* $Id: hsearch.h,v 1.14 2000/02/26 05:25:53 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -25,12 +25,15 @@
* whole lot of records per bucket or performance goes down.
*
* In a hash table allocated in shared memory, the directory cannot be
* expanded because it must stay at a fixed address.
* expanded because it must stay at a fixed address. The directory size
* should be selected using hash_select_dirsize (and you'd better have
* a good idea of the maximum number of entries!). For non-shared hash
* tables, the initial directory size can be left at the default.
*/
#define DEF_SEGSIZE 256
#define DEF_SEGSIZE_SHIFT 8/* log2(SEGSIZE) */
#define DEF_SEGSIZE_SHIFT 8 /* must be log2(DEF_SEGSIZE) */
#define DEF_DIRSIZE 256
#define DEF_FFACTOR 1/* default fill factor */
#define DEF_FFACTOR 1 /* default fill factor */
#define PRIME1 37 /* for the hash function */
#define PRIME2 1048583
......@@ -42,13 +45,13 @@
*/
typedef struct element
{
unsigned long next; /* secret from user */
unsigned long next; /* secret from user */
long key;
} ELEMENT;
typedef unsigned long BUCKET_INDEX;
/* segment is an array of bucket pointers */
/* segment is an array of bucket pointers */
typedef BUCKET_INDEX *SEGMENT;
typedef unsigned long SEG_OFFSET;
......@@ -65,10 +68,8 @@ typedef struct hashhdr
long nsegs; /* Number of allocated segments */
long keysize; /* hash key length in bytes */
long datasize; /* elem data length in bytes */
long max_dsize; /* 'dsize' limit if directory is fixed
* size */
BUCKET_INDEX freeBucketIndex;
/* index of first free bucket */
long max_dsize; /* 'dsize' limit if directory is fixed size */
BUCKET_INDEX freeBucketIndex; /* index of first free bucket */
#ifdef HASH_STATISTICS
long accesses;
long collisions;
......@@ -84,7 +85,6 @@ typedef struct htab
SEG_OFFSET *dir; /* 'directory' of segm starts */
long *(*alloc) (); /* memory allocator (long * for alignment
* reasons) */
} HTAB;
typedef struct hashctl
......@@ -115,7 +115,7 @@ typedef struct hashctl
#define HASH_ALLOC 0x100 /* Setting memory allocator */
/* seg_alloc assumes that INVALID_INDEX is 0*/
/* seg_alloc assumes that INVALID_INDEX is 0 */
#define INVALID_INDEX (0)
#define NO_MAX_DSIZE (-1)
/* number of hash buckets allocated at once */
......@@ -141,6 +141,7 @@ extern long *hash_search(HTAB *hashp, char *keyPtr, HASHACTION action,
bool *foundPtr);
extern long *hash_seq(HTAB *hashp);
extern long hash_estimate_size(long num_entries, long keysize, long datasize);
extern long hash_select_dirsize(long num_entries);
/*
* prototypes from functions in hashfn.c
......
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