Loop Optimizations for Acyclic Object-Oriented Queries

Nested loop execution of object-oriented queries retains the promise of maintaining the full generality of the object paradigm, independent of the speciics of any single object model. Thus, from this starting point we have developed an object-oriented query optimizer and execution engine. The methods, developed to date for only acyclic queries, augment nested loops structures with a simple marking mechanism such that unnecessary loop iterations are not repeated. In the case of acyclic queries, the executions are asymptotically optimal. In contrast to optimal query methods based on semijoin reductions our method involves no preprocessing step and thus avoids the extra I/O associated with semijoins and prevents the formal beneets of semijoin reduction from appearing as a practical improvement. Empirical results comparing our query environment with a commercially available product demonstrate signiicant performance improvement.