1. A data processing system implemented method of directing a data processing system to execute a query against a database having data objects, the query having sub-queries and having a union operator, the union operator operable on sub-queries associated with the query, the database being operatively coupled to the data processing system, the data processing system implemented method comprising: grouping the sub-queries of the union operator according to identified structural similarities, the identified structural similarities being based on an analysis of the sub-queries; grouping the data objects of the database according to the grouped sub-queries; replacing the grouped data objects and any sub-queries associated with the grouped data objects with a reference to a representative data object and a representative sub-query; and accessing at least one member of the grouped data objects, the accessing of the at least one member of the grouped data object being based on the reference.