NDLI: Least expected cost query optimization: what can we expect?

Content Provider	ACM Digital Library
Author	Halpern, Joseph Chu, Francis Gehrke, Johannes
Abstract	A standard assumption in the database query optimization literature is that it suffices to optimize for the "typical" case---that is, the case in which various parameters (e.g., the amount of available memory, the selectivities of predicates, etc.) take on their "typical" values. It was claimed in [CHS99] that we could do better by choosing plans based on their expected cost. Here we investigate this issue more thoroughly. We show that in many circumstances of interest, a "typical" value of the parameter often does give acceptable answers, provided that it is chosen carefully and we are interested only in minimizing expected running time. However, by minimizing the expected running time, we are effectively assuming that if plan $p^{1}$ runs three times as long as plan $p^{2},$ then $p^{1}$ is exactly three times as bad as $p^{2}.$ An assumption like this is not always appropriate. We show that focusing on least expected cost can lead to significant improvement for a number of cost functions of interest.
Starting Page	293
Ending Page	302
Page Count	10
File Format	PDF
ISBN	1581135076
DOI	10.1145/543613.543651
Language	English
Publisher	Association for Computing Machinery (ACM)
Publisher Date	2002-06-03
Publisher Place	New York
Access Restriction	Subscribed
Content Type	Text
Resource Type	Article

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Least expected cost query optimization: what can we expect?