Parallel Sub-collection Join Query Algorithms for a High Performance Object-Oriented Database Architecture

One of the differences between relational and object-oriented databases (OODB) is attributes in OODB can be of a collection type (e.g. sets, lists, arrays, bags) as well as a simple type (e.g. integer, string). Consequently, explicit join queries in OODB may be based on collection attributes. One form of collection join queries in OODB is sub-collection join queries, where the joins are based on collection attributes and the queries check for whether one collection is a sub-collection of the other. The sub-collection predicate can be in a form of subset, sublist, proper subset, or proper sublist. We propose two algorithms for parallel processing of sub-collection join queries. The first one is based on sort-mergenested-loop, whereas the second is based on sort-hash.