Algebraic transformation and optimization techniques have been the method of choice in relational query execution, but applying them in OODBMS is difficult due to the complexity of object-oriented query languages. This paper demonstrates that the problem can be simplified by mapping an OO data model to the binary ralational model implemented by Monet, a state-of-the-art database kernel. We present a generic mapping scheme to flatten data models and study the case of a straightforward object-oriented model. We show how flattening enabled us to implement a query algebra, using only a very limited set of simple operations. The required primitives and query execution strategies are discussed, and their performance is evaluated on the 1GB TPC-D benchmark, showing that our divide-and-conquerapproach yields excellent results.
Peter A. Boncz, Annita N. Wilschut, Martin L. Kers