Decomposition of SBQL queries for optimal result caching
Piotr Cybula, Kazimierz Subieta · 2011
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) which assumes description of semantics in the form of abstract implementation of query/programming language constructs. Pragmatic universality of object-oriented query language SBQL and its precise, formal operational semantics make it possible to investigate various crucial issues related to this kind of optimization. There are two main issues concerning this topic — the first is strategy for fast retrieval and high reuse of cached queries, the second issue is development of fast methods to recognize and maintain consistency of query results after database updates. This paper is focused on the first issue. We introduce data structures and algorithms for optimal, fast and transparent utilization of the result cache, involving methods of query normalization 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.