According to one embodiment of the present invention, a system for processing queries analyzes statistical information of input data records in relation to a first operation for a query. The system applies the first operation to a plurality of groups of input data records to produce corresponding groups of output data records, and coalesces the sets of output data records to form larger sets of data records for input to a subsequent second operation for the query based on the analysis. Embodiments of the present invention further include a method and computer program product for processing queries in substantially the same manners described above.