1. A computer implemented method, comprising: accessing a data source from which data will be retrieved via a plurality of processing threads, the data source having a plurality of records with each record being associated with a plurality of identifiers; dynamically evaluating each of the plurality of identifiers as a potential range identifier, wherein said evaluation is based at least in part on a number of distinct values present within each identifier; selecting one of the potential range identifiers as a selected range identifier; and dividing the plurality of records into ranges defined using the selected range identifier.