1. A computer-implemented method comprising: receiving an input query that relates to multiple attribute classes of data records having attribute classes associated therewith in data storage; identifying the multiple attribute classes related to the input query, the multiple attribute classes being a subset of less than all of the attribute classes associated with the data records in the data storage; accessing, from electronic storage, an index that is descriptive of the data records in the data storage, the index defining positional relationships between the attributes classes of the data records; identifying relative positions in the accessed index for the multiple attribute classes identified as being related to the input query; modifying the accessed index based on the identified relative positions, wherein modifying the accessed index based on the identified relative positions comprises: identifying portions of the accessed index that correspond to the multiple attribute classes identified as being related to the input query and removing portions of the accessed index that correspond to attribute classes other than the multiple attribute classes identified as being related to the input query; based on the identified relative positions, selecting, from among the multiple attribute classes identified as being related to the input query, the attribute class that has the highest relative position within the accessed index; and for each distinct value in the selected attribute class, assigning a distinct identifier to portions of the accessed index within the selected attribute class that correspond to the distinct value, identifying, using the modified index, groups of data records that are included in the data records in the data storage and that share common values for the multiple attribute classes identified as being related to the input query; accessing, from the data storage, metrics corresponding to the data records included in each of the identified groups of data records; performing computations on the accessed metrics that distinguish among each of the identified groups of data records; generating a report that reflects results of the computations; and storing, in electronic storage, the generated report.