Optimization of Object-Oriented Queries through Rewriting Compound Weakly Dependent Subqueries

摘要

A new static optimization method for object-oriented queries is presented. We deal with a special class of subqueries of a given query called "compound weakly dependent subqueries". The dependency is considered in the context of SBQL non-algebraic query operators like selection, projection, join, etc. A subquery is weakly dependent from its nearest non-algebraic operator if it depends only on expressions that can be entirely evaluated on small collections. The subquery is considered compound if the dependency concerns at least two such expressions. The research follows the stack-based approach (SBA) to query languages and its query language SBQL (Stack-Based Query Language). Our optimization method is based on analyzing scoping and binding rules for names occurring in queries.