Improve btree's initial-positioning-strategy code so that we never need

to step more than one entry after descending the search tree to arrive at
the correct place to start the scan.  This can improve the behavior
substantially when there are many entries equal to the chosen boundary
value.  Per suggestion from Dmitry Tkach, 14-Jul-03.

Author: tglsfdc

src/backend/access/nbtree/nbtinsert.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.109 2003/11/29 19:51:40 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.110 2003/12/21 01:23:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -86,8 +86,8 @@ _bt_doinsert(Relation rel, BTItem btitem,
 	itup_scankey = _bt_mkscankey(rel, itup);
 
 top:
-	/* find the page containing this key */
-	stack = _bt_search(rel, natts, itup_scankey, &buf, BT_WRITE);
+	/* find the first page containing this key */
+	stack = _bt_search(rel, natts, itup_scankey, false, &buf, BT_WRITE);
 
 	/* trade in our read lock for a write lock */
 	LockBuffer(buf, BUFFER_LOCK_UNLOCK);
@@ -100,7 +100,7 @@ _bt_doinsert(Relation rel, BTItem btitem,
 	 * need to move right in the tree.	See Lehman and Yao for an
 	 * excruciatingly precise description.
 	 */
-	buf = _bt_moveright(rel, buf, natts, itup_scankey, BT_WRITE);
+	buf = _bt_moveright(rel, buf, natts, itup_scankey, false, BT_WRITE);
 
 	/*
 	 * If we're not allowing duplicates, make sure the key isn't already
@@ -175,7 +175,7 @@ _bt_check_unique(Relation rel, BTItem btitem, Relation heapRel,
 	 * Find first item >= proposed new item.  Note we could also get a
 	 * pointer to end-of-page here.
 	 */
-	offset = _bt_binsrch(rel, buf, natts, itup_scankey);
+	offset = _bt_binsrch(rel, buf, natts, itup_scankey, false);
 
 	/*
 	 * Scan over all equal tuples, looking for live conflicts.
@@ -478,7 +478,7 @@ _bt_insertonpg(Relation rel,
 		if (movedright)
 			newitemoff = P_FIRSTDATAKEY(lpageop);
 		else
-			newitemoff = _bt_binsrch(rel, buf, keysz, scankey);
+			newitemoff = _bt_binsrch(rel, buf, keysz, scankey, false);
 	}
 
 	/*

src/backend/access/nbtree/nbtpage.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.73 2003/11/29 19:51:40 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.74 2003/12/21 01:23:06 tgl Exp $
  *
  *	NOTES
  *	   Postgres btree pages look like ordinary relation pages.	The opaque
@@ -804,7 +804,7 @@ _bt_pagedel(Relation rel, Buffer buf, bool vacuum_full)
 	/* we need a scan key to do our search, so build one */
 	itup_scankey = _bt_mkscankey(rel, &(targetkey->bti_itup));
 	/* find the leftmost leaf page containing this key */
-	stack = _bt_search(rel, rel->rd_rel->relnatts, itup_scankey,
+	stack = _bt_search(rel, rel->rd_rel->relnatts, itup_scankey, false,
 					   &lbuf, BT_READ);
 	/* don't need a pin on that either */
 	_bt_relbuf(rel, lbuf);