COMMON SUBEXPRESSION ISOLATION IN MULTIPLE QUERY OPTIMIZATION

Abstract

The simultaneous optimization of multiple queries submitted to a database system may lead to substantial savings over the current approach of optimizing each query separately. Isolating common subexpressions in multiple queries and treating their execution as a sharable resource are important prerequisites. This chapter presents techniques for recognizing, supporting, and exploiting common subexpressions in record-oriented, relational algebra, domain relational calculus, and tuple relational calculus query representations. It also investigates preconditions that transaction management mechanisms must satisfy to make multiple query optimization effective.