Micro-optimization of markpos() and restrpos() in btree and hash indexes.

Rather than using ReadBuffer() to increment the reference count on an
already-pinned buffer, we should use IncrBufferRefCount() as it is
faster and does not require acquiring the BufMgrLock.

Author: Neil Conway

src/backend/access/hash/hash.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.74 2004/11/11 00:32:40 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.75 2004/11/17 03:13:37 neilc Exp $
  *
  * NOTES
  *	  This file contains only the public interface routines.
@@ -397,9 +397,8 @@ hashmarkpos(PG_FUNCTION_ARGS)
 	/* bump pin count on currentItemData and copy to currentMarkData */
 	if (ItemPointerIsValid(&(scan->currentItemData)))
 	{
-		so->hashso_mrkbuf = _hash_getbuf(rel,
-								 BufferGetBlockNumber(so->hashso_curbuf),
-										 HASH_NOLOCK);
+		IncrBufferRefCount(so->hashso_curbuf);
+		so->hashso_mrkbuf = so->hashso_curbuf;
 		scan->currentMarkData = scan->currentItemData;
 	}
 
@@ -425,9 +424,8 @@ hashrestrpos(PG_FUNCTION_ARGS)
 	/* bump pin count on currentMarkData and copy to currentItemData */
 	if (ItemPointerIsValid(&(scan->currentMarkData)))
 	{
-		so->hashso_curbuf = _hash_getbuf(rel,
-								 BufferGetBlockNumber(so->hashso_mrkbuf),
-										 HASH_NOLOCK);
+		IncrBufferRefCount(so->hashso_mrkbuf);
+		so->hashso_curbuf = so->hashso_mrkbuf;
 		scan->currentItemData = scan->currentMarkData;
 	}
 

src/backend/access/nbtree/nbtree.c

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.121 2004/11/11 00:32:50 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.122 2004/11/17 03:13:38 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -477,8 +477,8 @@ btmarkpos(PG_FUNCTION_ARGS)
 	/* bump pin on current buffer for assignment to mark buffer */
 	if (ItemPointerIsValid(&(scan->currentItemData)))
 	{
-		so->btso_mrkbuf = ReadBuffer(scan->indexRelation,
-								  BufferGetBlockNumber(so->btso_curbuf));
+		IncrBufferRefCount(so->btso_curbuf);
+		so->btso_mrkbuf = so->btso_curbuf;
 		scan->currentMarkData = scan->currentItemData;
 		so->mrkHeapIptr = so->curHeapIptr;
 	}
@@ -509,8 +509,8 @@ btrestrpos(PG_FUNCTION_ARGS)
 	/* bump pin on marked buffer */
 	if (ItemPointerIsValid(&(scan->currentMarkData)))
 	{
-		so->btso_curbuf = ReadBuffer(scan->indexRelation,
-								  BufferGetBlockNumber(so->btso_mrkbuf));
+		IncrBufferRefCount(so->btso_mrkbuf);
+		so->btso_curbuf = so->btso_mrkbuf;
 		scan->currentItemData = scan->currentMarkData;
 		so->curHeapIptr = so->mrkHeapIptr;
 	}