Efficient Computation of Subqueries in Complex OLAP

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Efficient Computation of Subqueries in Complex OLAP
Expressing complex OLAP queries using group-by, aggregation, and joins can be extremely difficult. As a result of this, many alternate ways of expressing such queries have been developed by database researchers. The use of nested query expressions (subqueries in SQL), are a natural part of these techniques. Recent work has demonstrated how any nested query expression can be rewritten using algebraic operators. However, the solutions have focused on join/outer-join computations, which are not efficient in an OLAP context where huge fact tables are present. This paper proposes a technique that translates nested query expressions into an algebra extended with the GMDJ operator. The GMDJ is an operator with a simple and easy to optimize implementation that is particularly useful for OLAP computations because the size of intermediate results is bound by the size of the base-value argument relation. We show that all SQL subqueries can be expressed in the algebra using GMDJs. This not only m...
Michael H. Böhlen, Michael O. Akinde
Added 01 Nov 2009
Updated 01 Nov 2009
Type Conference
Year 2003
Where ICDE
Authors Michael H. Böhlen, Michael O. Akinde
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