Disclosed is a data processing system implemented method, a data processing system and an article of manufacture for executing a query having a union operator. The data processing system implemented method directs the data processing system to process a query against data objects. The data objects are operatively coupled to the data processing system. The query includes a parent operator. The parent operator references a union operator. The union operator references sub-queries. The sub-queries reference the data objects. The data processing system implemented method includes noting a set of partitionings for the union operator, the noted set of partitionings being based on the sub-queries and being based on the data objects reference by the sub-queries, and executing the query having the union operator, the execution of the query being based on the noted set of partitionings and the parent operator.