According to some embodiments, a data source is accessed from which data will be retrieved via a plurality of processing threads. The data source may have, for example, a plurality of records with each record being associated with a plurality of identifiers. Each of the plurality of identifiers may be dynamically evaluated as a potential range identifier, and the evaluation may be based at least in part on a number of distinct values present within each identifier. One of the potential range identifiers may be selected as a selected range identifier, and the plurality of records may be divided into ranges defined using the selected range identifier.