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Approximate String Joins in a Database (Almost) for Free -- Erratum

Gravano, Luis; Jagadish, H. V.; Ipeirotis, Panagiotis G.; Srivastava, Divesh; Koudas, Nick; Muthukrishnan, S.

In [GIJ+01a, GIJ+01b] we described how to use q-grams in an RDBMS to perform approximate string joins. We also showed how to implement the approximate join using plain SQL queries. Specifically, we described three filters, count filter, position filter, and length filter, which can be used to execute efficiently the approximate join. The intuition behind the count filter was that strings that are similar have many q-grams in common. In particular, two strings s1 and s2 can have up to max max {|s1|, |s2|} + q - 1 common q-grams. When s1 = s2, they have exactly that many q-grams in common. When s1 and s2 are within edit distance k, they share at least (max {|s1|, |s2|} + q - 1) - kq q-grams, since kq is the maximum numbers of q-grams that can be affected by k edit distance operations.

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Academic Units
Computer Science
Publisher
Department of Computer Science, Columbia University
Series
Columbia University Computer Science Technical Reports, CUCS-011-03
Published Here
April 26, 2011