Remove RelationGetBufferWithBuffer(), which is horribly confused about

appropriate pin-count manipulation, and instead use ReleaseAndReadBuffer.
Make use of the fact that the passed-in buffer (if there is one) must
be pinned to avoid grabbing the bufmgr spinlock when we are able to
return this same buffer.  Eliminate unnecessary 'previous tuple' and
'next tuple' fields of HeapScanDesc and IndexScanDesc, thereby removing
a whole lot of bookkeeping from heap_getnext() and related routines.

1 files changed, 26 insertions, 50 deletions

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index d5ff24df022..06abd2e8675 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.111 2001/05/12 19:58:27 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.112 2001/06/09 18:16:57 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -96,43 +96,6 @@ static int	ReleaseBufferWithBufferLock(Buffer buffer);
 static int	BufferReplace(BufferDesc *bufHdr);
 void		PrintBufferDescs(void);
 
-/* ---------------------------------------------------
- * RelationGetBufferWithBuffer
- *		see if the given buffer is what we want
- *		if yes, we don't need to bother the buffer manager
- * ---------------------------------------------------
- */
-Buffer
-RelationGetBufferWithBuffer(Relation relation,
-							BlockNumber blockNumber,
-							Buffer buffer)
-{
-	BufferDesc *bufHdr;
-
-	if (BufferIsValid(buffer))
-	{
-		if (!BufferIsLocal(buffer))
-		{
-			bufHdr = &BufferDescriptors[buffer - 1];
-			SpinAcquire(BufMgrLock);
-			if (bufHdr->tag.blockNum == blockNumber &&
-				RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node))
-			{
-				SpinRelease(BufMgrLock);
-				return buffer;
-			}
-			return ReadBufferInternal(relation, blockNumber, false, true);
-		}
-		else
-		{
-			bufHdr = &LocalBufferDescriptors[-buffer - 1];
-			if (bufHdr->tag.blockNum == blockNumber &&
-				RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node))
-				return buffer;
-		}
-	}
-	return ReadBufferInternal(relation, blockNumber, false, false);
-}
 
 /*
  * ReadBuffer -- returns a buffer containing the requested
@@ -141,7 +104,8 @@ RelationGetBufferWithBuffer(Relation relation,
  *		allocate a new block.
  *
  * Returns: the buffer number for the buffer containing
- *		the block read or NULL on an error.
+ *		the block read, or NULL on an error.  If successful,
+ *		the returned buffer has been pinned.
  *
  * Assume when this function is called, that reln has been
  *		opened already.
@@ -300,8 +264,8 @@ ReadBufferInternal(Relation reln, BlockNumber blockNum,
 }
 
 /*
- * BufferAlloc -- Get a buffer from the buffer pool but dont
- *		read it.
+ * BufferAlloc -- Get a buffer from the buffer pool but don't
+ *		read it.  If successful, the returned buffer is pinned.
  *
  * Returns: descriptor for buffer
  *
@@ -684,6 +648,11 @@ WriteNoReleaseBuffer(Buffer buffer)
  * Note: it is OK to pass buffer = InvalidBuffer, indicating that no old
  * buffer actually needs to be released.  This case is the same as ReadBuffer
  * except for the isExtend option.
+ *
+ * Also, if the passed buffer is valid and already contains the desired block
+ * number, we simply return it without ever acquiring the spinlock at all.
+ * Since the passed buffer must be pinned, it's OK to examine its block
+ * number without getting the lock first.
  */
 Buffer
 ReleaseAndReadBuffer(Buffer buffer,
@@ -698,12 +667,19 @@ ReleaseAndReadBuffer(Buffer buffer,
 		if (BufferIsLocal(buffer))
 		{
 			Assert(LocalRefCount[-buffer - 1] > 0);
+			bufHdr = &LocalBufferDescriptors[-buffer - 1];
+			if (bufHdr->tag.blockNum == blockNum &&
+				RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node))
+				return buffer;
 			LocalRefCount[-buffer - 1]--;
 		}
 		else
 		{
-			bufHdr = &BufferDescriptors[buffer - 1];
 			Assert(PrivateRefCount[buffer - 1] > 0);
+			bufHdr = &BufferDescriptors[buffer - 1];
+			if (bufHdr->tag.blockNum == blockNum &&
+				RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node))
+				return buffer;
 			if (PrivateRefCount[buffer - 1] > 1)
 				PrivateRefCount[buffer - 1]--;
 			else
@@ -1002,7 +978,7 @@ BufferPoolCheckLeak()
 			BufferDesc *buf = &(BufferDescriptors[i - 1]);
 
 			elog(NOTICE,
-				 "Buffer Leak: [%03d] (freeNext=%ld, freePrev=%ld, \
+				 "Buffer Leak: [%03d] (freeNext=%d, freePrev=%d, \
 relname=%s, blockNum=%d, flags=0x%x, refcount=%d %ld)",
 				 i - 1, buf->freeNext, buf->freePrev,
 				 buf->blind.relname, buf->tag.blockNum, buf->flags,
@@ -1396,7 +1372,7 @@ PrintBufferDescs()
 		SpinAcquire(BufMgrLock);
 		for (i = 0; i < NBuffers; ++i, ++buf)
 		{
-			elog(DEBUG, "[%02d] (freeNext=%ld, freePrev=%ld, relname=%s, \
+			elog(DEBUG, "[%02d] (freeNext=%d, freePrev=%d, relname=%s, \
 blockNum=%d, flags=0x%x, refcount=%d %ld)",
 				 i, buf->freeNext, buf->freePrev,
 				 buf->blind.relname, buf->tag.blockNum, buf->flags,
@@ -1426,7 +1402,7 @@ PrintPinnedBufs()
 	for (i = 0; i < NBuffers; ++i, ++buf)
 	{
 		if (PrivateRefCount[i] > 0)
-			elog(NOTICE, "[%02d] (freeNext=%ld, freePrev=%ld, relname=%s, \
+			elog(NOTICE, "[%02d] (freeNext=%d, freePrev=%d, relname=%s, \
 blockNum=%d, flags=0x%x, refcount=%d %ld)\n",
 				 i, buf->freeNext, buf->freePrev, buf->blind.relname,
 				 buf->tag.blockNum, buf->flags,
@@ -1719,7 +1695,7 @@ IncrBufferRefCount_Debug(char *file, int line, Buffer buffer)
 	{
 		BufferDesc *buf = &BufferDescriptors[buffer - 1];
 
-		fprintf(stderr, "PIN(Incr) %ld relname = %s, blockNum = %d, \
+		fprintf(stderr, "PIN(Incr) %d relname = %s, blockNum = %d, \
 refcount = %ld, file: %s, line: %d\n",
 				buffer, buf->blind.relname, buf->tag.blockNum,
 				PrivateRefCount[buffer - 1], file, line);
@@ -1737,7 +1713,7 @@ ReleaseBuffer_Debug(char *file, int line, Buffer buffer)
 	{
 		BufferDesc *buf = &BufferDescriptors[buffer - 1];
 
-		fprintf(stderr, "UNPIN(Rel) %ld relname = %s, blockNum = %d, \
+		fprintf(stderr, "UNPIN(Rel) %d relname = %s, blockNum = %d, \
 refcount = %ld, file: %s, line: %d\n",
 				buffer, buf->blind.relname, buf->tag.blockNum,
 				PrivateRefCount[buffer - 1], file, line);
@@ -1765,7 +1741,7 @@ ReleaseAndReadBuffer_Debug(char *file,
 	{
 		BufferDesc *buf = &BufferDescriptors[buffer - 1];
 
-		fprintf(stderr, "UNPIN(Rel&Rd) %ld relname = %s, blockNum = %d, \
+		fprintf(stderr, "UNPIN(Rel&Rd) %d relname = %s, blockNum = %d, \
 refcount = %ld, file: %s, line: %d\n",
 				buffer, buf->blind.relname, buf->tag.blockNum,
 				PrivateRefCount[buffer - 1], file, line);
@@ -1774,7 +1750,7 @@ refcount = %ld, file: %s, line: %d\n",
 	{
 		BufferDesc *buf = &BufferDescriptors[b - 1];
 
-		fprintf(stderr, "PIN(Rel&Rd) %ld relname = %s, blockNum = %d, \
+		fprintf(stderr, "PIN(Rel&Rd) %d relname = %s, blockNum = %d, \
 refcount = %ld, file: %s, line: %d\n",
 				b, buf->blind.relname, buf->tag.blockNum,
 				PrivateRefCount[b - 1], file, line);
@@ -2057,7 +2033,7 @@ LockBuffer(Buffer buffer, int mode)
 		{
 			S_UNLOCK(&(buf->cntx_lock));
 			RESUME_INTERRUPTS();
-			elog(ERROR, "UNLockBuffer: buffer %lu is not locked", buffer);
+			elog(ERROR, "UNLockBuffer: buffer %d is not locked", buffer);
 		}
 	}
 	else if (mode == BUFFER_LOCK_SHARE)