Using common subexpressions to optimize multiple queries

摘要

The problem of identifying common subexpressions and using them innthe simultaneous optimization of multiple queries is dealt with. Innparticular, emphasis is placed on the strategy of selecting access plansnfor single queries and their integration into a global access plan thatntakes advantage of common tasks. A dynamic programming algorithm isnpresented for the selection of individual access plans such that thenresulting global access plan is of minimum processing cost. Thencomputational complexity of this algorithm represents a significantnimprovement over existing algorithms