Advanced Query Processing in Object Bases Using Access Support Relations
Alfons Kemper, Guido Moerkotte · MADOC (University of Mannheim) · 1990
Even though the large body of knowledge of relational query optimization techniques can be utilized as a starting point for object-oriented query optimization the full exploitation of the object-oriented paradigm requires new, customized optimization techniques-not merely the assimilation of relational methods. This paper describes such an optimization strategy used in the GOM (Generic Object Model) project which combines established relational methods with new techniques designed for object models. The optimization method unites two concepts: (1) access support relations and (2) rule-bused query optimization. Access support relations constitute an index structure that is tailored for accessing objects along reference chains leading from one object to another via single-valued or set-valued attributes. The idea is to redundantly maintain frequently traversed reference chains separate from the object representation. The rule-based query optimizer generates for a declaratively stated query an evaluation plan that utilizes as much as possible the existing access support relations. Thii makes the exploitation of access support relations entirely transparent to the database user. The rule-based query optimizer is particularly amenable to incorporating search heuristics in order to prune the search space for an optimal (or near-optimal) query evaluation plan. Permission to copy without fee all or part of this material i granted provided that the topic arc not made or dktrihutcd lix direct commercial ad\antagc. the VLDB copbright notice and the title of the publication and its date appear. end notice is gi\cn that copying is hy permission of the Vcr) Large Data Bn\c Endowment. To copy othcrwisc. or to rcpuhli\h. require ;I kc and/or special permission from the Endowment. Proceedings of the 16th VLDB Conference Brisbane. Australia 1990