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VLDB
2001
ACM

Distinct Sampling for Highly-Accurate Answers to Distinct Values Queries and Event Reports

11 years 5 months ago
Distinct Sampling for Highly-Accurate Answers to Distinct Values Queries and Event Reports
Estimating the number of distinct values is a wellstudied problem, due to its frequent occurrence in queries and its importance in selecting good query plans. Previous work has shown powerful negative results on the quality of distinct-values estimates based on sampling (or other techniques that examine only part of the input data). We present an approach, called distinct sampling, that collects a specially tailored sample over the distinct values in the input, in a single scan of the data. In contrast to the previous negative results, our small Distinct Samples are guaranteed to accurately estimate the number of distinct values. The samples can be incrementally maintained up-to-date in the presence of data insertions and deletions, with minimal time and memory overheads, so that the full scan may be performed only once. Moreover, a stored Distinct Sample can be used to accurately estimate the number of distinct values within any range specified by the query, or within any other subs...
Phillip B. Gibbons
Added 30 Jul 2010
Updated 30 Jul 2010
Type Conference
Year 2001
Where VLDB
Authors Phillip B. Gibbons
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