*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.64 2005/03/18 16:16:09 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.65 2005/03/19 17:39:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"
#include "storage/smgr.h"
-#include "utils/relcache.h"
+#include "utils/memutils.h"
#include "utils/resowner.h"
/*#define LBDEBUG*/
+/* entry for buffer lookup hashtable */
+typedef struct
+{
+ BufferTag key; /* Tag of a disk page */
+ int id; /* Associated local buffer's index */
+} LocalBufferLookupEnt;
+
/* Note: this macro only works on local buffers, not shared ones! */
#define LocalBufHdrGetBlock(bufHdr) \
LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
-/* should be a GUC parameter some day */
-int NLocBuffer = 64;
+int NLocBuffer = 0; /* until buffers are initialized */
BufferDesc *LocalBufferDescriptors = NULL;
Block *LocalBufferBlockPointers = NULL;
static int nextFreeLocalBuf = 0;
+static HTAB *LocalBufHash = NULL;
+
/*
* LocalBufferAlloc -
- * allocate a local buffer. We do round robin allocation for now.
+ * Find or create a local buffer for the given page of the given relation.
*
* API is similar to bufmgr.c's BufferAlloc, except that we do not need
* to do any locking since this is all local. Also, IO_IN_PROGRESS
LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
{
BufferTag newTag; /* identity of requested block */
- int i;
- int trycounter;
+ LocalBufferLookupEnt *hresult;
BufferDesc *bufHdr;
+ int b;
+ int trycounter;
+ bool found;
INIT_BUFFERTAG(newTag, reln, blockNum);
- /* a low tech search for now -- should use a hashtable */
- for (i = 0; i < NLocBuffer; i++)
+ /* See if the desired buffer already exists */
+ hresult = (LocalBufferLookupEnt *)
+ hash_search(LocalBufHash, (void *) &newTag, HASH_FIND, NULL);
+
+ if (hresult)
{
- bufHdr = &LocalBufferDescriptors[i];
- if (BUFFERTAGS_EQUAL(bufHdr->tag, newTag))
- {
+ b = hresult->id;
+ bufHdr = &LocalBufferDescriptors[b];
+ Assert(BUFFERTAGS_EQUAL(bufHdr->tag, newTag));
#ifdef LBDEBUG
- fprintf(stderr, "LB ALLOC (%u,%d) %d\n",
- RelationGetRelid(reln), blockNum, -i - 1);
+ fprintf(stderr, "LB ALLOC (%u,%d) %d\n",
+ RelationGetRelid(reln), blockNum, -b - 1);
#endif
- LocalRefCount[i]++;
- ResourceOwnerRememberBuffer(CurrentResourceOwner,
- BufferDescriptorGetBuffer(bufHdr));
- if (bufHdr->flags & BM_VALID)
- *foundPtr = TRUE;
- else
- {
- /* Previous read attempt must have failed; try again */
- *foundPtr = FALSE;
- }
- return bufHdr;
+ LocalRefCount[b]++;
+ ResourceOwnerRememberBuffer(CurrentResourceOwner,
+ BufferDescriptorGetBuffer(bufHdr));
+ if (bufHdr->flags & BM_VALID)
+ *foundPtr = TRUE;
+ else
+ {
+ /* Previous read attempt must have failed; try again */
+ *foundPtr = FALSE;
}
+ return bufHdr;
}
#ifdef LBDEBUG
trycounter = NLocBuffer;
for (;;)
{
- int b = nextFreeLocalBuf;
+ b = nextFreeLocalBuf;
if (++nextFreeLocalBuf >= NLocBuffer)
nextFreeLocalBuf = 0;
(char *) LocalBufHdrGetBlock(bufHdr),
true);
+ /* Mark not-dirty now in case we error out below */
+ bufHdr->flags &= ~BM_DIRTY;
+
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 not dirty.
*/
if (LocalBufHdrGetBlock(bufHdr) == NULL)
{
- char *data = (char *) malloc(BLCKSZ);
+ char *data;
- if (data == NULL)
- ereport(ERROR,
- (errcode(ERRCODE_OUT_OF_MEMORY),
- errmsg("out of memory")));
+ data = (char *) MemoryContextAlloc(TopMemoryContext, BLCKSZ);
- /*
- * Set pointer for use by BufferGetBlock() macro.
- */
+ /* Set pointer for use by BufferGetBlock() macro */
LocalBufHdrGetBlock(bufHdr) = (Block) data;
}
+ /*
+ * Update the hash table: remove old entry, if any, and make new one.
+ */
+ if (bufHdr->flags & BM_TAG_VALID)
+ {
+ hresult = (LocalBufferLookupEnt *)
+ hash_search(LocalBufHash, (void *) &bufHdr->tag,
+ HASH_REMOVE, NULL);
+ if (!hresult) /* shouldn't happen */
+ elog(ERROR, "local buffer hash table corrupted");
+ /* mark buffer invalid just in case hash insert fails */
+ CLEAR_BUFFERTAG(bufHdr->tag);
+ bufHdr->flags &= ~(BM_VALID | BM_TAG_VALID);
+ }
+
+ hresult = (LocalBufferLookupEnt *)
+ hash_search(LocalBufHash, (void *) &newTag, HASH_ENTER, &found);
+ if (!hresult)
+ ereport(ERROR,
+ (errcode(ERRCODE_OUT_OF_MEMORY),
+ errmsg("out of memory")));
+ if (found) /* shouldn't happen */
+ elog(ERROR, "local buffer hash table corrupted");
+ hresult->id = b;
+
/*
* it's all ours now.
*/
void
InitLocalBuffer(void)
{
+ int nbufs = 64; /* should be from a GUC var */
+ HASHCTL info;
int i;
- /*
- * these aren't going away. I'm not gonna use palloc.
- */
+ /* Create the lookup hash table */
+ MemSet(&info, 0, sizeof(info));
+ info.keysize = sizeof(BufferTag);
+ info.entrysize = sizeof(LocalBufferLookupEnt);
+ info.hash = tag_hash;
+
+ LocalBufHash = hash_create("Local Buffer Lookup Table",
+ nbufs,
+ &info,
+ HASH_ELEM | HASH_FUNCTION);
+
+ if (!LocalBufHash)
+ elog(ERROR, "could not initialize local buffer hash table");
+
+ /* Allocate and zero buffer headers and auxiliary arrays */
LocalBufferDescriptors = (BufferDesc *)
- calloc(NLocBuffer, sizeof(*LocalBufferDescriptors));
+ MemoryContextAllocZero(TopMemoryContext,
+ nbufs * sizeof(BufferDesc));
LocalBufferBlockPointers = (Block *)
- calloc(NLocBuffer, sizeof(*LocalBufferBlockPointers));
+ MemoryContextAllocZero(TopMemoryContext,
+ nbufs * sizeof(Block));
LocalRefCount = (int32 *)
- calloc(NLocBuffer, sizeof(*LocalRefCount));
+ MemoryContextAllocZero(TopMemoryContext,
+ nbufs * sizeof(int32));
+
nextFreeLocalBuf = 0;
- for (i = 0; i < NLocBuffer; i++)
+ /* initialize fields that need to start off nonzero */
+ for (i = 0; i < nbufs; i++)
{
BufferDesc *buf = &LocalBufferDescriptors[i];
*/
buf->buf_id = -i - 2;
}
+
+ /* Initialization done, mark buffers allocated */
+ NLocBuffer = nbufs;
}
/*
AtProcExit_LocalBuffers(void)
{
/* just zero the refcounts ... */
- MemSet(LocalRefCount, 0, NLocBuffer * sizeof(*LocalRefCount));
+ if (LocalRefCount)
+ MemSet(LocalRefCount, 0, NLocBuffer * sizeof(*LocalRefCount));
}
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