1. A method in a computing device for identifying an object similar to a target object, the method comprising: for a plurality of features of objects, generating a cluster index data structure for a collection of objects, the cluster index data structure defining clusters of objects that are feature similar based on the feature; for each feature, identifying, from the cluster index data structure for that feature, candidate objects that are feature similar to the target object based on that feature; and for candidate objects, indicating similarity of the candidate object to the target object based on features for which the candidate object is feature similar to the target object.