When implementing persistent objects on a relational database, a major performance issue is prefetching data to minimize the number of roundtrips to the database. This is especially hard with navigational applicatons, since future accesses are unpredictable. We propose using the context in which an object is loaded as a predictor of future acceses, where context can be a stored collection of relationships, a query result, or a complex object. When an object O's context is prefetched. We present a design for maintaining context and using it to guide prefetch. We give performance measurements of its implementation in Microsoft Repository, showing up to a 70percent reduction in running time. We describe variations that selectively apply the technique, exploit asynchronous access, and use application-supplied performance hints.
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