Techniques for bushy tree execution plans for snowstorm schema

摘要

Methods for transforming a query to simulate a bushy tree execution plan for queries containing joins in series are provided. Left deep tree execution plans are supported by most relational database systems but are inefficient at processing queries directed to databases with snowstorm schema. A snowstorm schema contains several large fact tables and many smaller dimension tables, which make reference to one another. Bushy tree execution plans can be much more efficient for processing queries to snowstorm schema. The decision to choose between left-deep and bushy tree execution plans are based on the relative costs of the two execution plans. The methods provided transform queries which are otherwise executed with left deep tree execution plans into queries which are executed with simulated bushy tree execution plans.