1 files changed, 103 insertions, 2 deletions

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index c4ea6aa612..c30d7d56ac 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 1.27 1998/07/27 19:37:40 vadim Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtree.c,v 1.28 1998/07/30 05:04:49 vadim Exp $
  *
  * NOTES
  *	  This file contains only the public interface routines.
@@ -44,6 +44,8 @@ bool		BuildingBtree = false;		/* see comment in btbuild() */
 bool		FastBuild = true;	/* use sort/build instead of insertion
 								 * build */
 
+static void	_bt_restscan(IndexScanDesc scan);
+
 /*
  *	btbuild() -- build a new btree index.
  *
@@ -374,8 +376,10 @@ btinsert(Relation rel, Datum *datum, char *nulls, ItemPointer ht_ctid, Relation
 	pfree(btitem);
 	pfree(itup);
 
+#if 0
 	/* adjust any active scans that will be affected by this insertion */
 	_bt_adjscans(rel, &(res->pointerData), BT_INSERT);
+#endif
 
 	return (res);
 }
@@ -395,10 +399,28 @@ 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
+		 */
+		_bt_restscan(scan);
 		res = _bt_next(scan, dir);
+	}
 	else
 		res = _bt_first(scan, dir);
-
+	
+	/* Save heap TID to use it in _bt_restscan */
+	if (res)
+		((BTScanOpaque)scan->opaque)->curHeapIptr = res->heap_iptr;
+	
 	return ((char *) res);
 }
 
@@ -555,6 +577,7 @@ btmarkpos(IndexScanDesc scan)
 								   BufferGetBlockNumber(so->btso_curbuf),
 									 BT_READ);
 		scan->currentMarkData = scan->currentItemData;
+		so->mrkHeapIptr = so->curHeapIptr;
 	}
 }
 
@@ -585,6 +608,7 @@ btrestrpos(IndexScanDesc scan)
 									 BT_READ);
 
 		scan->currentItemData = scan->currentMarkData;
+		so->curHeapIptr = so->mrkHeapIptr;
 	}
 }
 
@@ -598,3 +622,80 @@ btdelete(Relation rel, ItemPointer 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)
+{
+	Relation		rel = scan->relation;
+	BTScanOpaque	so = (BTScanOpaque) scan->opaque;
+	Buffer			buf = so->btso_curbuf;
+	Page			page = BufferGetPage(buf);
+	ItemPointer		current = &(scan->currentItemData);
+	OffsetNumber	offnum = ItemPointerGetOffsetNumber(current),
+					maxoff = PageGetMaxOffsetNumber(page);
+	BTPageOpaque	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
+	ItemPointerData	target = so->curHeapIptr;
+	BTItem			item;
+	BlockNumber		blkno;
+
+	if (maxoff >= offnum)
+	{
+		/* 
+		 * if the item is where we left it or has just moved right 
+		 * on this page, we're done 
+		 */
+		for ( ;
+			 offnum <= maxoff;
+			 offnum = OffsetNumberNext(offnum))
+		{
+			item = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
+			if (item->bti_itup.t_tid.ip_blkid.bi_hi == \
+					target.ip_blkid.bi_hi && \
+				item->bti_itup.t_tid.ip_blkid.bi_lo == \
+					target.ip_blkid.bi_lo && \
+				item->bti_itup.t_tid.ip_posid == target.ip_posid)
+			{
+				current->ip_posid = offnum;
+				return;
+			}
+		}
+	}
+
+	/* 
+	 * By here, the item we're looking for moved right at least one page 
+	 */
+	for (;;)
+	{
+		if (P_RIGHTMOST(opaque))
+			elog(FATAL, "_bt_restscan: my bits moved right off the end of the world!");
+
+		blkno = opaque->btpo_next;
+		_bt_relbuf(rel, buf, BT_READ);
+		buf = _bt_getbuf(rel, blkno, BT_READ);
+		page = BufferGetPage(buf);
+		maxoff = PageGetMaxOffsetNumber(page);
+		opaque = (BTPageOpaque) PageGetSpecialPointer(page);
+
+		/* see if it's on this page */
+		for (offnum = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY ;
+			 offnum <= maxoff;
+			 offnum = OffsetNumberNext(offnum))
+		{
+			item = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
+			if (item->bti_itup.t_tid.ip_blkid.bi_hi == \
+					target.ip_blkid.bi_hi && \
+				item->bti_itup.t_tid.ip_blkid.bi_lo == \
+					target.ip_blkid.bi_lo && \
+				item->bti_itup.t_tid.ip_posid == target.ip_posid)
+			{
+				ItemPointerSet(current, blkno, offnum);
+				so->btso_curbuf = buf;
+				return;
+			}
+		}
+	}
+}