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/*-------------------------------------------------------------------------
*
* buf_table.c
* routines for finding buffers in the buffer pool.
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.32 2003/11/13 14:57:15 wieck Exp $
*
*-------------------------------------------------------------------------
*/
/*
* OLD COMMENTS
*
* Data Structures:
*
* Buffers are identified by their BufferTag (buf.h). This
* file contains routines for allocating a shmem hash table to
* map buffer tags to buffer descriptors.
*
* Synchronization:
*
* All routines in this file assume BufMgrLock is held by their caller.
*/
#include "postgres.h"
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"
static HTAB *SharedBufHash;
/*
* Initialize shmem hash table for mapping buffers
*/
void
InitBufTable(int size)
{
HASHCTL info;
/* assume lock is held */
/* BufferTag maps to Buffer */
info.keysize = sizeof(BufferTag);
info.entrysize = sizeof(BufferLookupEnt);
info.hash = tag_hash;
SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table",
size, size,
&info,
HASH_ELEM | HASH_FUNCTION);
if (!SharedBufHash)
elog(FATAL, "could not initialize shared buffer hash table");
}
/*
* BufTableLookup
*/
int
BufTableLookup(BufferTag *tagPtr)
{
BufferLookupEnt *result;
if (tagPtr->blockNum == P_NEW)
return -1;
result = (BufferLookupEnt *)
hash_search(SharedBufHash, (void *) tagPtr, HASH_FIND, NULL);
if (!result)
return -1;
return result->id;
}
/*
* BufTableDelete
*/
bool
BufTableInsert(BufferTag *tagPtr, Buffer buf_id)
{
BufferLookupEnt *result;
bool found;
result = (BufferLookupEnt *)
hash_search(SharedBufHash, (void *) tagPtr, HASH_ENTER, &found);
if (!result)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory")));
if (found) /* found something else in the table? */
elog(ERROR, "shared buffer hash table corrupted");
result->id = buf_id;
return TRUE;
}
/*
* BufTableDelete
*/
bool
BufTableDelete(BufferTag *tagPtr)
{
BufferLookupEnt *result;
result = (BufferLookupEnt *)
hash_search(SharedBufHash, (void *) tagPtr, HASH_REMOVE, NULL);
if (!result) /* shouldn't happen */
elog(ERROR, "shared buffer hash table corrupted");
return TRUE;
}
/* prints out collision stats for the buf table */
#ifdef NOT_USED
void
DBG_LookupListCheck(int nlookup)
{
nlookup = 10;
hash_stats("Shared", SharedBufHash);
}
#endif
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