Evaluating Functional Joins Along Nested Reference Sets in Object-Relational and Object-Oriented Databases
Reinhard Braumandl, Jens Christian Claussen, Alfons Kemper · 1998
Previous work on functional joins was constrained in two ways: (1) all approaches we know assume references being implemented as physical object identifiers (OIDs) and (2) most approaches are, in addition, limited to single-valued reference attributes. Both are severe limitations since most object-relational and all object-oriented database systems do support nested reference sets and many object systems do implement references as location-independent (logical) OIDs. In this work, we develop a new functional join algorithm that can be used for any realization form for OIDs (physical or logical) and is particularly geared towards supporting functional joins along nested reference sets. The algorithm can be applied to evaluate joins along arbitrarily long path expressions which may include one or more reference sets. The new algorithm generalizes previously proposed partition-based pointer joins by repeatedly applying partitioning with interleaved re-merging before evaluating the next fu...