Create a routine PageIndexMultiDelete() that replaces a loop around

PageIndexTupleDelete() with a single pass of compactification ---
logic mostly lifted from PageRepairFragmentation.  I noticed while
profiling that a VACUUM that's cleaning up a whole lot of deleted
tuples would spend as much as a third of its CPU time in
PageIndexTupleDelete; not too surprising considering the loop method
was roughly O(N^2) in the number of tuples involved.

2 files changed, 5 insertions, 15 deletions

diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c
index 3e2a9010a44..2b82a87a1d4 100644
--- a/src/backend/access/nbtree/nbtpage.c
+++ b/src/backend/access/nbtree/nbtpage.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.81 2004/12/31 21:59:22 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.82 2005/03/22 06:17:03 tgl Exp $
  *
  *	NOTES
  *	   Postgres btree pages look like ordinary relation pages.	The opaque
@@ -639,17 +639,12 @@ _bt_delitems(Relation rel, Buffer buf,
 			 OffsetNumber *itemnos, int nitems)
 {
 	Page		page = BufferGetPage(buf);
-	int			i;
 
 	/* No ereport(ERROR) until changes are logged */
 	START_CRIT_SECTION();
 
-	/*
-	 * Delete the items in reverse order so we don't have to think about
-	 * adjusting item numbers for previous deletions.
-	 */
-	for (i = nitems - 1; i >= 0; i--)
-		PageIndexTupleDelete(page, itemnos[i]);
+	/* Fix the page */
+	PageIndexMultiDelete(page, itemnos, nitems);
 
 	/* XLOG stuff */
 	if (!rel->rd_istemp)
diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 0bd2c418f03..ade60619a3d 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 1.19 2004/12/31 21:59:22 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.20 2005/03/22 06:17:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -411,12 +411,7 @@ btree_xlog_delete(bool redo, XLogRecPtr lsn, XLogRecord *record)
 		unused = (OffsetNumber *) ((char *) xlrec + SizeOfBtreeDelete);
 		unend = (OffsetNumber *) ((char *) xlrec + record->xl_len);
 
-		/* be careful to delete from back to front */
-		while (unused < unend)
-		{
-			unend--;
-			PageIndexTupleDelete(page, *unend);
-		}
+		PageIndexMultiDelete(page, unused, unend - unused);
 	}
 
 	PageSetLSN(page, lsn);