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.
This commit is contained in:
Tom Lane
parent
c05abfb1a8
commit
08b1040374
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.48 2000/01/26 05:56:58 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.49 2000/02/26 05:25:55 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -332,7 +332,7 @@ ShmemIsValid(unsigned long addr)
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HTAB *
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ShmemInitHash(char *name, /* table string name for shmem index */
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long init_size, /* initial table size */
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long max_size, /* max size of the table (NOT USED) */
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long max_size, /* max size of the table */
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HASHCTL *infoP, /* info about key and bucket size */
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int hash_flags) /* info about infoP */
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{
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@ -340,19 +340,21 @@ ShmemInitHash(char *name, /* table string name for shmem index */
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long *location;
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/*
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* Hash tables allocated in shared memory have a fixed directory; it
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* can't grow or other backends wouldn't be able to find it. The
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* segbase is for calculating pointer values. The shared memory
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* Hash tables allocated in shared memory have a fixed directory;
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* it can't grow or other backends wouldn't be able to find it.
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* So, make sure we make it big enough to start with.
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*
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* The segbase is for calculating pointer values. The shared memory
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* allocator must be specified too.
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*/
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infoP->dsize = infoP->max_dsize = DEF_DIRSIZE;
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infoP->dsize = infoP->max_dsize = hash_select_dirsize(max_size);
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infoP->segbase = (long *) ShmemBase;
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infoP->alloc = ShmemAlloc;
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hash_flags |= HASH_SHARED_MEM | HASH_DIRSIZE;
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/* look it up in the shmem index */
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location = ShmemInitStruct(name,
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sizeof(HHDR) + DEF_DIRSIZE * sizeof(SEG_OFFSET),
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sizeof(HHDR) + infoP->dsize * sizeof(SEG_OFFSET),
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&found);
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/*
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/hash/dynahash.c,v 1.28 2000/01/26 05:57:24 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/hash/dynahash.c,v 1.29 2000/02/26 05:25:54 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -328,10 +328,7 @@ init_htab(HTAB *hashp, int nelem)
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{
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*segp = seg_alloc(hashp);
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if (*segp == (SEG_OFFSET) 0)
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{
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hash_destroy(hashp);
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return 0;
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}
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return -1;
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}
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#if HASH_DEBUG
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@ -392,6 +389,34 @@ hash_estimate_size(long num_entries, long keysize, long datasize)
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return size;
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}
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/*
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* Select an appropriate directory size for a hashtable with the given
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* maximum number of entries.
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* This is only needed for hashtables in shared memory, whose directories
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* cannot be expanded dynamically.
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* NB: assumes that all hash structure parameters have default values!
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*
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* XXX this had better agree with the behavior of init_htab()...
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*/
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long
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hash_select_dirsize(long num_entries)
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{
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long nBuckets,
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nSegments,
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nDirEntries;
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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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/* # of segments needed for nBuckets */
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nSegments = 1L << my_log2((nBuckets - 1) / DEF_SEGSIZE + 1);
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/* directory entries */
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nDirEntries = DEF_DIRSIZE;
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while (nDirEntries < nSegments)
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nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
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return nDirEntries;
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}
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/********************** DESTROY ROUTINES ************************/
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@ -1,13 +1,13 @@
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/*-------------------------------------------------------------------------
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*
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* hsearch.h
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* for hashing in the new buffer manager
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* for hash tables, particularly hash tables in shared memory
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*
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*
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: hsearch.h,v 1.13 2000/01/26 05:58:38 momjian Exp $
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* $Id: hsearch.h,v 1.14 2000/02/26 05:25:53 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -25,12 +25,15 @@
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* whole lot of records per bucket or performance goes down.
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*
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* In a hash table allocated in shared memory, the directory cannot be
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* expanded because it must stay at a fixed address.
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* expanded because it must stay at a fixed address. The directory size
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* should be selected using hash_select_dirsize (and you'd better have
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* a good idea of the maximum number of entries!). For non-shared hash
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* tables, the initial directory size can be left at the default.
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*/
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#define DEF_SEGSIZE 256
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#define DEF_SEGSIZE_SHIFT 8/* log2(SEGSIZE) */
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#define DEF_SEGSIZE_SHIFT 8 /* must be log2(DEF_SEGSIZE) */
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#define DEF_DIRSIZE 256
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#define DEF_FFACTOR 1/* default fill factor */
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#define DEF_FFACTOR 1 /* default fill factor */
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#define PRIME1 37 /* for the hash function */
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#define PRIME2 1048583
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@ -42,13 +45,13 @@
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*/
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typedef struct element
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{
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unsigned long next; /* secret from user */
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unsigned long next; /* secret from user */
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long key;
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} ELEMENT;
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typedef unsigned long BUCKET_INDEX;
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/* segment is an array of bucket pointers */
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/* segment is an array of bucket pointers */
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typedef BUCKET_INDEX *SEGMENT;
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typedef unsigned long SEG_OFFSET;
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@ -65,10 +68,8 @@ typedef struct hashhdr
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long nsegs; /* Number of allocated segments */
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long keysize; /* hash key length in bytes */
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long datasize; /* elem data length in bytes */
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long max_dsize; /* 'dsize' limit if directory is fixed
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* size */
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BUCKET_INDEX freeBucketIndex;
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/* index of first free bucket */
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long max_dsize; /* 'dsize' limit if directory is fixed size */
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BUCKET_INDEX freeBucketIndex; /* index of first free bucket */
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#ifdef HASH_STATISTICS
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long accesses;
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long collisions;
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@ -84,7 +85,6 @@ typedef struct htab
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SEG_OFFSET *dir; /* 'directory' of segm starts */
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long *(*alloc) (); /* memory allocator (long * for alignment
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* reasons) */
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} HTAB;
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typedef struct hashctl
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@ -115,7 +115,7 @@ typedef struct hashctl
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#define HASH_ALLOC 0x100 /* Setting memory allocator */
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/* seg_alloc assumes that INVALID_INDEX is 0*/
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/* seg_alloc assumes that INVALID_INDEX is 0 */
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#define INVALID_INDEX (0)
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#define NO_MAX_DSIZE (-1)
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/* number of hash buckets allocated at once */
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@ -141,6 +141,7 @@ extern long *hash_search(HTAB *hashp, char *keyPtr, HASHACTION action,
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bool *foundPtr);
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extern long *hash_seq(HTAB *hashp);
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extern long hash_estimate_size(long num_entries, long keysize, long datasize);
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extern long hash_select_dirsize(long num_entries);
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/*
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* prototypes from functions in hashfn.c
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