Clean up WAL/buffer interactions as per my recent proposal. Get rid of the

misleadingly-named WriteBuffer routine, and instead require routines that
change buffer pages to call MarkBufferDirty (which does exactly what it says).
We also require that they do so before calling XLogInsert; this takes care of
the synchronization requirement documented in SyncOneBuffer.  Note that
because bufmgr takes the buffer content lock (in shared mode) while writing
out any buffer, it doesn't matter whether MarkBufferDirty is executed before
the buffer content change is complete, so long as the content change is
completed before releasing exclusive lock on the buffer.  So it's OK to set
the dirtybit before we fill in the LSN.
This eliminates the former kluge of needing to set the dirtybit in LockBuffer.
Aside from making the code more transparent, we can also add some new
debugging assertions, in particular that the caller of MarkBufferDirty must
hold the buffer content lock, not merely a pin.

1 files changed, 6 insertions, 11 deletions

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 84dad045a7..59c733330b 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/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 1.142 2006/03/05 15:58:21 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.143 2006/03/31 23:32:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -624,18 +624,13 @@ btbulkdelete(PG_FUNCTION_ARGS)
 				}
 			}
 
-			/*
-			 * If we need to delete anything, do it and write the buffer; else
-			 * just release the buffer.
-			 */
-			nextpage = opaque->btpo_next;
+			/* Apply any needed deletes */
 			if (ndeletable > 0)
-			{
 				_bt_delitems(rel, buf, deletable, ndeletable);
-				_bt_wrtbuf(rel, buf);
-			}
-			else
-				_bt_relbuf(rel, buf);
+
+			/* Fetch nextpage link before releasing the buffer */
+			nextpage = opaque->btpo_next;
+			_bt_relbuf(rel, buf);
 
 			/* call vacuum_delay_point while not holding any buffer lock */
 			vacuum_delay_point();