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170 lines
3.2 KiB
C
170 lines
3.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* buf_table.c--
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* routines for finding buffers in the buffer pool.
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.11 1998/06/15 19:29:09 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* OLD COMMENTS
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*
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* Data Structures:
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*
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* Buffers are identified by their BufferTag (buf.h). This
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* file contains routines for allocating a shmem hash table to
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* map buffer tags to buffer descriptors.
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*
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* Synchronization:
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*
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* All routines in this file assume buffer manager spinlock is
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* held by their caller.
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*/
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#include "postgres.h"
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#include "storage/bufmgr.h"
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#include "storage/buf_internals.h" /* where the declarations go */
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#include "storage/shmem.h"
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#include "storage/spin.h"
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#include "utils/hsearch.h"
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static HTAB *SharedBufHash;
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typedef struct lookup
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{
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BufferTag key;
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Buffer id;
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} LookupEnt;
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/*
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* Initialize shmem hash table for mapping buffers
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*/
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void
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InitBufTable()
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{
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HASHCTL info;
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int hash_flags;
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/* assume lock is held */
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/* BufferTag maps to Buffer */
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info.keysize = sizeof(BufferTag);
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info.datasize = sizeof(Buffer);
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info.hash = tag_hash;
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hash_flags = (HASH_ELEM | HASH_FUNCTION);
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SharedBufHash = (HTAB *) ShmemInitHash("Shared Buf Lookup Table",
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NBuffers, NBuffers,
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&info, hash_flags);
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if (!SharedBufHash)
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{
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elog(FATAL, "couldn't initialize shared buffer pool Hash Tbl");
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exit(1);
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}
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}
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BufferDesc *
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BufTableLookup(BufferTag *tagPtr)
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{
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LookupEnt *result;
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bool found;
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if (tagPtr->blockNum == P_NEW)
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return (NULL);
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result = (LookupEnt *)
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hash_search(SharedBufHash, (char *) tagPtr, HASH_FIND, &found);
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if (!result)
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{
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elog(ERROR, "BufTableLookup: BufferLookup table corrupted");
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return (NULL);
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}
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if (!found)
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return (NULL);
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return (&(BufferDescriptors[result->id]));
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}
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/*
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* BufTableDelete
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*/
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bool
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BufTableDelete(BufferDesc *buf)
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{
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LookupEnt *result;
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bool found;
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/*
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* buffer not initialized or has been removed from table already.
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* BM_DELETED keeps us from removing buffer twice.
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*/
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if (buf->flags & BM_DELETED)
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return (TRUE);
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buf->flags |= BM_DELETED;
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result = (LookupEnt *)
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hash_search(SharedBufHash, (char *) &(buf->tag), HASH_REMOVE, &found);
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if (!(result && found))
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{
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elog(ERROR, "BufTableDelete: BufferLookup table corrupted");
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return (FALSE);
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}
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return (TRUE);
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}
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bool
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BufTableInsert(BufferDesc *buf)
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{
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LookupEnt *result;
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bool found;
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/* cannot insert it twice */
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Assert(buf->flags & BM_DELETED);
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buf->flags &= ~(BM_DELETED);
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result = (LookupEnt *)
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hash_search(SharedBufHash, (char *) &(buf->tag), HASH_ENTER, &found);
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if (!result)
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{
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Assert(0);
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elog(ERROR, "BufTableInsert: BufferLookup table corrupted");
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return (FALSE);
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}
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/* found something else in the table ! */
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if (found)
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{
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Assert(0);
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elog(ERROR, "BufTableInsert: BufferLookup table corrupted");
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return (FALSE);
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}
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result->id = buf->buf_id;
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return (TRUE);
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}
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/* prints out collision stats for the buf table */
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#ifdef NOT_USED
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void
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DBG_LookupListCheck(int nlookup)
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{
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nlookup = 10;
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hash_stats("Shared", SharedBufHash);
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}
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#endif
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