Validated cost models for parallel OQL query processing

Sampaio, SDM; Paton, NW; Smith, J; Watson, P

doi:10.1007/3-540-46102-7_10

Validated cost models for parallel OQL query processing

Lookup NU author(s): Professor Paul Watson ORCiD

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Abstract

Query cost models are widely used, both for performance analysis and for comparing execution plans during query optimisation. In essence, a cost model predicts where time is being spent during query evaluation. Although many cost models have been proposed, for serial, parallel and distributed database systems, surprisingly few of these have been validated against real systems. This paper presents cost models for the parallel evaluation of ODMG OQL queries, which have been compared with experimental results obtained using the Polar object database system. The paper describes the validation of the cost model for a collection of queries, using three join algorithms over the 007 benchmark database. The results show that the cost model generally both ranks alternative plans appropriately, and gives a useful indication of the response times that can be expected from a plan. The paper also illustrates the application of the cost model by highlighting the contributions of different features and operations to query response times.