Query Optimization by Result Caching in the Stack-Based Approach

摘要

We present a new approach to optimization of query languages using cached results of previously evaluated queries. It is based on the stack-based approach (SBA) and object-oriented query language SBQL. SBA assumes description of semantics in the form of abstract implementation of query/programming language constructs. Pragmatic universality of SBQL and its precise, formal operational semantics make it possible to investigate various crucial issues related to this kind of optimization. Two main issues are: organization of the cache enabling fast retrieval of cached queries and development of fast methods to recognize consistency of queries and incremental altering of cached query results after database updates. This paper is focused on the first issue concerning optimal, fast and transparent utilization of the result cache, involving methods of query normalization enabling higher reuse of cached queries with preservation of original query semantics and decomposition of complex queries into smaller ones. We present experimental results of the optimization that demonstrate the effectiveness of our technique.