77 *
88 *
99 * IDENTIFICATION
10- * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.3 1996/10/23 07:39:00 scrappy Exp $
10+ * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.4 1996/10/25 09:55:36 scrappy Exp $
1111 *
1212 *-------------------------------------------------------------------------
1313 */
@@ -815,7 +815,8 @@ _bt_itemcmp(Relation rel,
815815
816816/*
817817 *_bt_updateitem() -- updates the key of the item identified by the
818- * oid with the key of newItem (done in place)
818+ * oid with the key of newItem (done in place if
819+ * possible)
819820 *
820821 */
821822static void
@@ -829,14 +830,17 @@ _bt_updateitem(Relation rel,
829830OffsetNumber maxoff ;
830831OffsetNumber i ;
831832ItemPointerData itemPtrData ;
832- BTItem item ;
833+ BTItem item , itemCopy ;
833834IndexTuple oldIndexTuple ,newIndexTuple ;
835+ int newSize ,oldSize ,first ;
834836
835837page = BufferGetPage (buf );
836838maxoff = PageGetMaxOffsetNumber (page );
837839
838840/* locate item on the page */
839- i = P_HIKEY ;
841+ first = P_RIGHTMOST ((BTPageOpaque )PageGetSpecialPointer (page )) \
842+ ?P_HIKEY :P_FIRSTKEY ;
843+ i = first ;
840844do {
841845item = (BTItem )PageGetItem (page ,PageGetItemId (page ,i ));
842846i = OffsetNumberNext (i );
@@ -849,9 +853,46 @@ _bt_updateitem(Relation rel,
849853
850854oldIndexTuple = & (item -> bti_itup );
851855newIndexTuple = & (newItem -> bti_itup );
852-
853- /* keep the original item pointer */
854- ItemPointerCopy (& (oldIndexTuple -> t_tid ),& itemPtrData );
855- CopyIndexTuple (newIndexTuple ,& oldIndexTuple );
856- ItemPointerCopy (& itemPtrData ,& (oldIndexTuple -> t_tid ));
856+ oldSize = DOUBLEALIGN (IndexTupleSize (oldIndexTuple ));
857+ newSize = DOUBLEALIGN (IndexTupleSize (newIndexTuple ));
858+ #ifdef NBTINSERT_PATCH_DEBUG
859+ printf ("_bt_updateitem: newSize=%d, oldSize=%d\n" ,newSize ,oldSize );
860+ #endif
861+
862+ /*
863+ * If new and old item have the same size do the update in place
864+ * and return.
865+ */
866+ if (oldSize == newSize ) {
867+ /* keep the original item pointer */
868+ ItemPointerCopy (& (oldIndexTuple -> t_tid ),& itemPtrData );
869+ CopyIndexTuple (newIndexTuple ,& oldIndexTuple );
870+ ItemPointerCopy (& itemPtrData ,& (oldIndexTuple -> t_tid ));
871+ return ;
872+ }
873+
874+ /*
875+ * If new and old items have different size the update in place
876+ * is not possible. In this case the old item is deleted and the
877+ * new one is inserted.
878+ * The new insertion should be done using _bt_insertonpg which
879+ * would also takes care of the page splitting if needed, but
880+ * unfortunately it doesn't work, so PageAddItem is used instead.
881+ * There is the possibility that there is not enough space in the
882+ * page and the item is not inserted.
883+ */
884+ itemCopy = palloc (newSize );
885+ memmove ((char * )itemCopy , (char * )newItem ,newSize );
886+ itemCopy -> bti_oid = item -> bti_oid ;
887+ newIndexTuple = & (itemCopy -> bti_itup );
888+ ItemPointerCopy (& (oldIndexTuple -> t_tid ),& (newIndexTuple -> t_tid ));
889+
890+ /*
891+ * Get the offset number of the item then delete it and insert
892+ * the new item in the same place.
893+ */
894+ i = OffsetNumberPrev (i );
895+ PageIndexTupleDelete (page ,i );
896+ PageAddItem (page , (Item )itemCopy ,newSize ,i ,LP_USED );
897+ pfree (itemCopy );
857898}