A detailed database statistics model for distributed query processing (relational, boolean expression, retrieval, access paths)
Balakrishnan Muthuswamy · 1984
This study develops an approach to distributed query optimization which uses detailed database statistics regarding database instances. A Detailed Database Statistics Model (DDSM) is presented which (1) portrays statistics about a relational database in matrix notation, and (2) presents matrix algebra on the statistics, suitable for query optimization. The model is applicable to centralized as well as distributed database systems that support the relational model of data. The typical assumptions of uniformly distributed attribute values, and independence among attributes are relaxed. Since computed statistics about the database are used, the model is expected to enable accurate evaluation of query processing alternatives and thus better query processing strategies. Results of a simulation study to evaluate the performance of the model and the matrix operations are also presented. The DDSM can be used in conjunction with existing query optimization algorithms, and existing local processing and/or data transfer cost models. A discussion of such interfacing is presented in the appendix.