Abstract: - Counts of database unique values are crucial information in query optimization. Estimating the number of the distinct values occurs frequently in database queries, due to its importance in selecting query plans. We present a nonparametric method for estimating the database distincts, and, then, the number of distinct values. The method computes few parameters which describe the distribution of distances of distinct values in the attribute value ranges. Tests have been carried out that also show the useful applicability of the method to estimate equi-join selectivity factors.
Estimation of Database Unique Values
LEFONS, Ezio;TANGORRA, Filippo
2004-01-01
Abstract
Abstract: - Counts of database unique values are crucial information in query optimization. Estimating the number of the distinct values occurs frequently in database queries, due to its importance in selecting query plans. We present a nonparametric method for estimating the database distincts, and, then, the number of distinct values. The method computes few parameters which describe the distribution of distances of distinct values in the attribute value ranges. Tests have been carried out that also show the useful applicability of the method to estimate equi-join selectivity factors.File in questo prodotto:
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