|
Abstract : |
1 Introduction Traditional work on algebraic query optimization has mainly focused on the problem of ordering joins in a query. Restrictions like selections and projections are generally treated by "push-down rules". According to these, selections and projections should be pushed down the query plan as far as possible. These heuristic rules worked quite well for traditional relational database systems where the evaluation of selection predicates is of neglectable cost and every selection reduces the cost of subsequent joins. As pointed out by Hellerstein, Stonebraker [5], this is no longer true for modern database systems like object-oriented DBMSs? Research supported by the German Research Association (DFG) under contract, |
