Integrating a Maximum-Entropy Cardinality Estimator into DB2 UDB

摘要

When comparing alternative query execution plans (QEPs), a cost-based query optimizer in a relational database management system (RDBMS) needs to estimate the selectivity of conjunctive predicates. The optimizer immediately faces a challenging problem: how to combine available partial information about selectivities in a consistent and comprehensive manner, This paper describes a prototype solution to this problem.