Patent ID: 8560550

Claim:
A computer based method executed by one or more processors, the method comprising: receiving a search query comprising at least one phrase at a server that is in communication with an index server system that includes: (a) a primary index server system that stores a primary index including primary phrase posting lists, each primary phrase posting list being associated with a phrase and including up to a maximum number of documents that contain the phrase and comprising references to documents in rank order based on relevance of the phrase to each respective document and (b) a secondary index server system including secondary phrase posting lists, each secondary phrase posting list being associated with a primary phrase posting list in the primary index, and including documents that contain the phrase that is associated with the primary phrase posting list in the primary index and which have relevance scores less than the relevance score of a lowest ranked document in the primary posting list for the phrase; responsive to the search query containing a first phrase having a primary posting list and a secondary posting list and a second phrase having only a primary posting list, intersecting the primary posting list of the first phrase with the primary posting list of the second phrase to obtain a first set of common documents, and intersecting the secondary posting list of the first phrase with the primary posting list of the second phrase to obtain a second set of common documents, and conjoining the first and second sets of common documents to provide a result set; and ranking the common documents in the result set.