1. A computer implemented method for indexing documents with respect to a phrase, wherein each document as a document identifier, the method comprising: establishing a list of documents that contain the phrase; ranking the documents in the list by a relevance score; storing a first portion of the list comprising higher ranked documents in a primary index in rank order of the relevance scores; and storing a second portion of the list comprising lesser ranked documents in a secondary index in numerical order of the document identifiers.