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19 Feb 2003

Histograms for Selectivity Estimation
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Speaker: HO Wai Shing

 

Abstract Many modules, such as query optimizers, in a DBMS require an accurate estimate of the selectivity of queries. Histograms are one of the most commonly stored statistics for selectivity estimation. They take reasonably small amount of space and their estimates are quite accurate.

A histogram approximates a data distribution by grouping the data values into buckets, and approximate the actual distribution by the statistics stored in each bucket. Different types of histograms are proposed in the literature. In this talk we will discuss a taxonomy of existing histograms for signle-dimensional data. Few extensions of histograms for multi-dimensional data will also be discussed.

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