Parallel double sort-merge algorithm for object-oriented collection join queries

In object-oriented databases (OODBs), although path expressions through pointer connections may exist, it is sometimes necessary to perform an explicit join operation between two classes. Since a class may contain collection attributes as well as simple attributes, join queries in OODBs may be based on collections. A need for collection join algorithms arises, since the conventional join algorithms (such as hybrid-hash join and GRACE join) were not designed for collection join queries. A new algorithm called the "parallel double sort-merge" join algorithm is proposed. This algorithm plays an important role in parallel object-oriented query processing, due to its superiority over the conventional join methods.