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.
Bibliographical noteFunding Information:
* Corresponding author. E-mail addresses: firstname.lastname@example.org (S. Cohen), email@example.com (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).
- Full disjunction
- Incomplete information
- Null values
- Query processing