Query Optimization using Horizontal Class Partitioning in Object Oriented Databases

Query processing remains one of the most important challenges of object oriented database systems (OODBSs). A cost model for query processing is very useful in performing the physical query optimization. Horizontal class partitioning (HCP) is a technique for reducing the number of disk accesses for executing a given set of queries by minimizing the number of irrelevant object instances accessed. Moreover, its importance in reduction of query execution time has been widely acknowledged. However, existing cost models for query processing in OODBSs do not take into consideration the HCP criteria. In this paper, we present an analytical cost model for query execution for unpartitioned and horizontally partitioned classes. This cost is necessary for deciding whether to use HCP or to keep all classes unpartitioned. The effect of HCP upon the query execution process is analyzed. Key Words : Object-oriented database, horizontal class partitioning, cost model, query processing, query optimizat..