Holes in joins

13 years 7 months ago
Holes in joins
A join of two relations in real databases is usually much smaller than their cartesian product. This means that most of the combinations of tuples in the crossproduct of the respective relations do not appear together in the join result. We characterize these combinations as ranges of attributes that do not appear together. We sketch an algorithm for finding such combinations and present experimental results from real data sets. We then explore two potential applications of this knowledge in query processing. In the first application, we model empty joins as materialized views, we show how they can be used for query optimization. In the second application, we propose a strategy that uses information about empty joins for an improved join selectivity estimation.
Jarek Gryz, Dongming Liang
Added 13 Dec 2010
Updated 13 Dec 2010
Type Journal
Year 2006
Where JIIS
Authors Jarek Gryz, Dongming Liang
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