1. A computer-implemented method of querying an index of first objects comprised of a plurality of cells index entries and a pool of second objects, the method comprising: evaluating the index of the first objects to produce a group of one or more candidates based on whether one or more index entries of the first objects satisfy cells designated in a query that respective first objects in the index overlap; adding second objects from the pool to said group of candidates to produce an interim group of candidates; filtering the interim group of candidates by comparing the query with approximations of the candidates of the interim group with the query to produce filtered candidate objects; determining if the filtered candidate objects satisfy the query by comparing the first and second objects corresponding to the filtered candidate objects with the query; and in response to determining that the filtered candidate objects satisfy the query, returning a result.