From fdf6be80f993d2908f794c0a33aedff479a92813 Mon Sep 17 00:00:00 2001
From: "Vadim B. Mikheev" <vadim4o@yahoo.com>
Date: Sun, 28 Mar 1999 20:32:42 +0000
Subject: 1. Vacuum is updated for MVCC. 2. Much faster btree tuples deletion
 in the case when first on page    index tuple is deleted (no movement to the
 left page(s)). 3. Remember blkno of new root page in BTPageOpaque of   
 left/right siblings when root page is splitted.

---
 src/backend/access/nbtree/nbtree.c | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

(limited to 'src/backend/access/nbtree/nbtree.c')

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 5ae59ccf12..2ded78b1a6 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtree.c,v 1.36 1999/02/21 03:48:27 scrappy Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtree.c,v 1.37 1999/03/28 20:31:58 vadim Exp $
  *
  * NOTES
  *	  This file contains only the public interface routines.
@@ -372,11 +372,6 @@ btinsert(Relation rel, Datum *datum, char *nulls, ItemPointer ht_ctid, Relation
 	pfree(btitem);
 	pfree(itup);
 
-#ifdef NOT_USED
-	/* adjust any active scans that will be affected by this insertion */
-	_bt_adjscans(rel, &(res->pointerData), BT_INSERT);
-#endif
-
 	return res;
 }
 
@@ -396,15 +391,9 @@ btgettuple(IndexScanDesc scan, ScanDirection dir)
 
 	if (ItemPointerIsValid(&(scan->currentItemData)))
 	{
-
 		/*
-		 * Now we don't adjust scans on insertion (comments in
-		 * nbtscan.c:_bt_scandel()) and I hope that we will unlock current
-		 * index page before leaving index in LLL: this means that current
-		 * index tuple could be moved right before we get here and we have
-		 * to restore our scan position. We save heap TID pointed by
-		 * current index tuple and use it. This will work untill we start
-		 * to re-use (move heap tuples) without vacuum... - vadim 07/29/98
+		 * Restore scan position using heap TID returned 
+		 * by previous call to btgettuple().
 		 */
 		_bt_restscan(scan);
 		res = _bt_next(scan, dir);
@@ -612,16 +601,12 @@ void
 btdelete(Relation rel, ItemPointer tid)
 {
 	/* adjust any active scans that will be affected by this deletion */
-	_bt_adjscans(rel, tid, BT_DELETE);
+	_bt_adjscans(rel, tid);
 
 	/* delete the data from the page */
 	_bt_pagedel(rel, tid);
 }
 
-/*
- * Reasons are in btgettuple... We have to find index item that
- * points to heap tuple returned by previous call to btgettuple().
- */
 static void
 _bt_restscan(IndexScanDesc scan)
 {
@@ -637,6 +622,20 @@ _bt_restscan(IndexScanDesc scan)
 	BTItem		item;
 	BlockNumber blkno;
 
+	/*
+	 * We use this as flag when first index tuple on page
+	 * is deleted but we do not move left (this would
+	 * slowdown vacuum) - so we set current->ip_posid
+	 * before first index tuple on the current page
+	 * (_bt_step will move it right)...
+	 */
+	if (!ItemPointerIsValid(&target))
+	{
+		ItemPointerSetOffsetNumber(&(scan->currentItemData), 
+			OffsetNumberPrev(P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY));
+		return;
+	}
+
 	if (maxoff >= offnum)
 	{
 
-- 
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