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Another round of code cleanup on bufmgr. Use BM_VALID flag to keep track

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of whether we have successfully read data into a buffer; this makes the
error behavior a bit more transparent (IMHO anyway), and also makes it
work correctly for local buffers which don't use Start/TerminateBufferIO.
Collapse three separate functions for writing a shared buffer into one.
This overlaps a bit with cleanups that Neil proposed awhile back, but
seems not to have committed yet.
This commit is contained in:
Tom Lane
2004-04-21 18:06:30 +00:00
parent aeee856564
commit 95a03e9cdf
6 changed files with 331 additions and 431 deletions
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34
src/backend/storage/buffer/localbuf.c
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.52 2004/02/10 01:55:25 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.53 2004/04/21 18:06:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -36,19 +36,25 @@ static int nextFreeLocalBuf = 0;
/*
* LocalBufferAlloc -
* allocate a local buffer. We do round robin allocation for now.
*
* API is similar to bufmgr.c's BufferAlloc, except that we do not need
* to have the BufMgrLock since this is all local. Also, IO_IN_PROGRESS
* does not get set.
*/
BufferDesc *
LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
{
BufferTag newTag; /* identity of requested block */
int i;
BufferDesc *bufHdr = NULL;
BufferDesc *bufHdr;
INIT_BUFFERTAG(newTag, reln, blockNum);
/* 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)
bufHdr = &LocalBufferDescriptors[i];
if (BUFFERTAGS_EQUAL(bufHdr->tag, newTag))
{
#ifdef LBDEBUG
fprintf(stderr, "LB ALLOC (%u,%d) %d\n",
@@ -56,8 +62,14 @@ LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
#endif
LocalRefCount[i]++;
*foundPtr = TRUE;
return &LocalBufferDescriptors[i];
if (bufHdr->flags & BM_VALID)
*foundPtr = TRUE;
else
{
/* Previous read attempt must have failed; try again */
*foundPtr = FALSE;
}
return bufHdr;
}
}
@@ -67,6 +79,7 @@ LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
#endif
/* need to get a new buffer (round robin for now) */
bufHdr = NULL;
for (i = 0; i < NLocBuffer; i++)
{
int b = (nextFreeLocalBuf + i) % NLocBuffer;
@@ -108,7 +121,7 @@ LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
*
* 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.
* the buffer as not dirty.
*/
if (bufHdr->data == (SHMEM_OFFSET) 0)
{
@@ -135,9 +148,8 @@ LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
/*
* it's all ours now.
*/
bufHdr->tag.rnode = reln->rd_node;
bufHdr->tag.blockNum = blockNum;
bufHdr->flags &= ~BM_DIRTY;
bufHdr->tag = newTag;
bufHdr->flags &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED | BM_IO_ERROR);
bufHdr->cntxDirty = false;
*foundPtr = FALSE;