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Summary: CORDS: Automatic Discovery of Correlations
and Soft Functional Dependencies
Ihab F. Ilyas1
Volker Markl2
Peter Haas2
Paul Brown2
Ashraf Aboulnaga2
1
Purdue University 2
IBM Almaden Research Center
250 N. University Street 650 Harry Road, K55/B1
West Lafayette, Indiana, 47906 San Jose, CA, 95139
ilyas@cs.purdue.edu marklv,phaas,pbrown1,aashraf@us.ibm.com
ABSTRACT
The rich dependency structure found in the columns of real-world
relational databases can be exploited to great advantage, but can
also cause query optimizers--which usually assume that columns
are statistically independent--to underestimate the selectivities
of conjunctive predicates by orders of magnitude. We introduce
cords, an efficient and scalable tool for automatic discovery of
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