Prefetching based on the type-level access pattern in object-relational DBMSs

Prefetching is an effective method for minimizing the number of round-trips between the client and the server in database management systems. We propose new notions of the type-level access locality and the type-level access pattern. We also formally define the notions of capturing and prefetching to help understand the underlying mechanisms. We then develop an efficient prefetching policy based on these notions and the framework. The type-level access locality is a phenomenon that repetitive patterns exist in the attributes referenced. The type-level access pattern is a pattern of attributes that are referenced in accessing the objects. Existing prefetching methods are based on object-level or page-level access patterns, which consist of object-ids or page-ids of the objects accessed. However the drawback of these methods is that they work only when exactly the same objects or pages are accessed repeatedly. In contrast even though the same objects are not accessed repeatedly our technique effectively prefetches objects if the same attributes are referenced repeatedly, i.e., if there is type-level access locality. Many navigational applications in object-relational database management systems (ORDBMSs) have type-level access locality. Therefore, our technique can be employed in ORDBMSs to effectively reduce the number of round trips, thereby significantly enhancing the performance.