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/*-------------------------------------------------------------------------
*
* localbuf.c
* local buffer manager. Fast buffer manager for temporary tables,
* which never need to be WAL-logged or checkpointed, etc.
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994-5, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/localbuf.c,v 1.49 2003/08/04 02:40:03 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"
#include "storage/smgr.h"
#include "utils/relcache.h"
/*#define LBDEBUG*/
/* should be a GUC parameter some day */
int NLocBuffer = 64;
BufferDesc *LocalBufferDescriptors = NULL;
Block *LocalBufferBlockPointers = NULL;
long *LocalRefCount = NULL;
static int nextFreeLocalBuf = 0;
/*
* LocalBufferAlloc -
* allocate a local buffer. We do round robin allocation for now.
*/
BufferDesc *
LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
{
int i;
BufferDesc *bufHdr = (BufferDesc *) NULL;
/* a low tech search for now -- not optimized for scans */
for (i = 0; i < NLocBuffer; i++)
{
if (LocalBufferDescriptors[i].tag.rnode.relNode ==
reln->rd_node.relNode &&
LocalBufferDescriptors[i].tag.blockNum == blockNum)
{
#ifdef LBDEBUG
fprintf(stderr, "LB ALLOC (%u,%d) %d\n",
RelationGetRelid(reln), blockNum, -i - 1);
#endif
LocalRefCount[i]++;
*foundPtr = TRUE;
return &LocalBufferDescriptors[i];
}
}
#ifdef LBDEBUG
fprintf(stderr, "LB ALLOC (%u,%d) %d\n",
RelationGetRelid(reln), blockNum, -nextFreeLocalBuf - 1);
#endif
/* need to get a new buffer (round robin for now) */
for (i = 0; i < NLocBuffer; i++)
{
int b = (nextFreeLocalBuf + i) % NLocBuffer;
if (LocalRefCount[b] == 0)
{
bufHdr = &LocalBufferDescriptors[b];
LocalRefCount[b]++;
nextFreeLocalBuf = (b + 1) % NLocBuffer;
break;
}
}
if (bufHdr == NULL)
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
errmsg("no empty local buffer available")));
/*
* this buffer is not referenced but it might still be dirty. if
* that's the case, write it out before reusing it!
*/
if (bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
{
Relation bufrel = RelationNodeCacheGetRelation(bufHdr->tag.rnode);
/* flush this page */
if (bufrel == (Relation) NULL)
{
smgrblindwrt(DEFAULT_SMGR,
bufHdr->tag.rnode,
bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data));
}
else
{
smgrwrite(DEFAULT_SMGR, bufrel,
bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data));
/* drop refcount incremented by RelationNodeCacheGetRelation */
RelationDecrementReferenceCount(bufrel);
}
LocalBufferFlushCount++;
}
/*
* lazy memory allocation: allocate space on first use of a buffer.
*
* Note this path cannot be taken for a buffer that was previously in
* use, so it's okay to do it (and possibly error out) before marking
* the buffer as valid.
*/
if (bufHdr->data == (SHMEM_OFFSET) 0)
{
char *data = (char *) malloc(BLCKSZ);
if (data == NULL)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory")));
/*
* This is a bit of a hack: bufHdr->data needs to be a shmem
* offset for consistency with the shared-buffer case, so make it
* one even though it's not really a valid shmem offset.
*/
bufHdr->data = MAKE_OFFSET(data);
/*
* Set pointer for use by BufferGetBlock() macro.
*/
LocalBufferBlockPointers[-(bufHdr->buf_id + 2)] = (Block) data;
}
/*
* it's all ours now.
*
* We need not in tblNode currently but will in future I think, when
* we'll give up rel->rd_fd to fmgr cache.
*/
bufHdr->tag.rnode = reln->rd_node;
bufHdr->tag.blockNum = blockNum;
bufHdr->flags &= ~BM_DIRTY;
bufHdr->cntxDirty = false;
*foundPtr = FALSE;
return bufHdr;
}
/*
* WriteLocalBuffer -
* writes out a local buffer (actually, just marks it dirty)
*/
void
WriteLocalBuffer(Buffer buffer, bool release)
{
int bufid;
Assert(BufferIsLocal(buffer));
#ifdef LBDEBUG
fprintf(stderr, "LB WRITE %d\n", buffer);
#endif
bufid = -(buffer + 1);
LocalBufferDescriptors[bufid].flags |= BM_DIRTY;
if (release)
{
Assert(LocalRefCount[bufid] > 0);
LocalRefCount[bufid]--;
}
}
/*
* InitLocalBuffer -
* init the local buffer cache. Since most queries (esp. multi-user ones)
* don't involve local buffers, we delay allocating actual memory for the
* buffers until we need them; just make the buffer headers here.
*/
void
InitLocalBuffer(void)
{
int i;
/*
* these aren't going away. I'm not gonna use palloc.
*/
LocalBufferDescriptors =
(BufferDesc *) calloc(NLocBuffer, sizeof(BufferDesc));
LocalBufferBlockPointers = (Block *) calloc(NLocBuffer, sizeof(Block));
LocalRefCount = (long *) calloc(NLocBuffer, sizeof(long));
nextFreeLocalBuf = 0;
for (i = 0; i < NLocBuffer; i++)
{
BufferDesc *buf = &LocalBufferDescriptors[i];
/*
* negative to indicate local buffer. This is tricky: shared
* buffers start with 0. We have to start with -2. (Note that the
* routine BufferDescriptorGetBuffer adds 1 to buf_id so our first
* buffer id is -1.)
*/
buf->buf_id = -i - 2;
}
}
/*
* AtEOXact_LocalBuffers - clean up at end of transaction.
*
* This is just like AtEOXact_Buffers, but for local buffers.
*/
void
AtEOXact_LocalBuffers(bool isCommit)
{
int i;
for (i = 0; i < NLocBuffer; i++)
{
if (LocalRefCount[i] != 0)
{
BufferDesc *buf = &(LocalBufferDescriptors[i]);
if (isCommit)
elog(WARNING,
"local buffer leak: [%03d] (rel=%u/%u, blockNum=%u, flags=0x%x, refcount=%d %ld)",
i,
buf->tag.rnode.tblNode, buf->tag.rnode.relNode,
buf->tag.blockNum, buf->flags,
buf->refcount, LocalRefCount[i]);
LocalRefCount[i] = 0;
}
}
}
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