How Good Are Query Optimizers, Really?
Leis V, Gubichev A, Mirchev A, Boncz P, Kemper A, Neumann T (2016)
Publication Type: Conference contribution
Publication year: 2016
Publisher: Association for Computing Machinery
Book Volume: 9
Pages Range: 204-215
Conference Proceedings Title: Proceedings of the VLDB Endowment
Event location: Delhi
Abstract
Finding a good join order is crucial for query performance. In this paper, we introduce the Join Order Benchmark (JOB) and experimentally revisit the main components in the classic query optimizer architecture using a complex, real-world data set and realistic multi-join queries. We investigate the quality of industrial-strength cardinality estimators and find that all estimators routinely produce large errors. We further show that while estimates are essential for finding a good join order, query performance is unsatisfactory if the query engine relies too heavily on these estimates. Using another set of experiments that measure the impact of the cost model, we find that it has much less influence on query performance than the cardinality estimates. Finally, we investigate plan enumeration techniques comparing exhaustive dynamic programming with heuristic algorithms and find that exhaustive enumeration improves performance despite the sub-optimal cardinality estimates. © 2015 VLDB.
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Germany (DE)How to cite
APA:
Leis, V., Gubichev, A., Mirchev, A., Boncz, P., Kemper, A., & Neumann, T. (2016). How Good Are Query Optimizers, Really? In Proceedings of the VLDB Endowment (pp. 204-215). Delhi, IN: Association for Computing Machinery.
MLA:
Leis, Viktor, et al. "How Good Are Query Optimizers, Really?" Proceedings of the 42nd International Conference on Very Large Data Bases, VLDB 2016, Delhi Association for Computing Machinery, 2016. 204-215.
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