Optimization of Queries in the Object-Oriented Database Involving Path Expression

Abstract

Despite the fact that many forms of path indexes-indexes on path expression-have been proposed for fast
processing of object-oriented queries, there has been little study on query optimization that fully utilizes
path indexes. In this paper we first explore some of the problems that are encountered when trying to
optimize queries in an object-oriented database in connection with path expression. Further we minimize
the problem of indexing of path expression by taking out common path subexpression that can identify a
common subquery in a query so as to compute it only once and then reuse its result is a popular optimization
technique and the path indices that relate entities in the beginning of path expressions with entities occurring
in the end of those expression and the path between such entities. Taking inspiration from the success of
query optimization in the relational model, our methodology has enriched existing optimization techniques
to handle the new notions offered by object oriented databases.