Abstract
The full disjunction is a variation of the join operator that maximally combines tuples from connected relations, while preserving all information in the relations. The full disjunction can be seen as a natural extension of the binary outerjoin operator to an arbitrary number of relations and is a useful operator for information integration. This paper presents the algorithm IncrementalFD for computing the full disjunction of a set of relations. IncrementalFD improves upon previous algorithms for computing the full disjunction in four ways. First, it has a lower total runtime when computing the full result and a lower runtime when computing only k tuples of the result, for any constant k. Second, for a natural class of ranking functions, IncrementalFD can be adapted to return tuples in ranking order. Third, a variation of IncrementalFD can be used to return approximate full disjunctions (which contain maximal approximately join consistent tuples). Fourth, IncrementalFD can be adapted to have a block-based execution, instead of a tuple-based execution.
Original language | American English |
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Pages (from-to) | 648-668 |
Number of pages | 21 |
Journal | Journal of Computer and System Sciences |
Volume | 73 |
Issue number | 4 |
DOIs | |
State | Published - Jun 2007 |
Externally published | Yes |
Bibliographical note
Funding Information:* Corresponding author. E-mail addresses: sarac@ie.technion.ac.il (S. Cohen), sagiv@cs.huji.ac.il (Y. Sagiv). URL: http://iew3.technion.ac.il/~sarac (S. Cohen). 1 The author was partially supported by Israel Science Foundation (Grant 1032/05). 2 The author was partially supported by Israel Science Foundation (Grant 893/05).
Keywords
- Approximate
- Full disjunction
- Incomplete information
- Null values
- Outer-join
- Query processing
- Ranking