Use of graph-theoretic models for optimal relational database accesses to perform join

Abstract

A graph model is presented to analyze the performance of a relational join. The amount of page reaccesses, the page access sequence, and the amount of buffer needed are represented in terms of graph parameters. By using the graph model formed from the index on the join attributes, we determine the relationships between these parameters. Two types of buffer allocation strategies are studied, and the upper bound on the buffer size with no page reaccess is given. This bound is shown to be the maximum cut value of a graph. Hence, the problem of computing this upper bound is NP-hard. We also give algorithms to determine a page access sequence requiring a near optimal buffer size with no page reaccess. The optimal page access sequence for a fixed buffer size has also been considered.