Modify btree to delete known-dead index entries without an actual VACUUM.

When we are about to split an index page to do an insertion, first look
to see if any entries marked LP_DELETE exist on the page, and if so remove
them to try to make enough space for the desired insert.  This should reduce
index bloat in heavily-updated tables, although of course you still need
VACUUM eventually to clean up the heap.

Junji Teramoto

1 files changed, 9 insertions, 1 deletions

diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 63cb342e393..126f593cd96 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.35 2006/07/14 14:52:17 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.36 2006/07/25 19:13:00 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -346,6 +346,7 @@ btree_xlog_delete(XLogRecPtr lsn, XLogRecord *record)
 	Relation	reln;
 	Buffer		buffer;
 	Page		page;
+	BTPageOpaque opaque;
 
 	if (record->xl_info & XLR_BKP_BLOCK_1)
 		return;
@@ -374,6 +375,13 @@ btree_xlog_delete(XLogRecPtr lsn, XLogRecord *record)
 		PageIndexMultiDelete(page, unused, unend - unused);
 	}
 
+	/*
+	 * Mark the page as not containing any LP_DELETE items --- see comments
+	 * in _bt_delitems().
+	 */
+	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
+	opaque->btpo_flags &= ~BTP_HAS_GARBAGE;
+
 	PageSetLSN(page, lsn);
 	PageSetTLI(page, ThisTimeLineID);
 	MarkBufferDirty(buffer);