21. A method, comprising: at a computing device having one or more processors and memory: identifying a plurality of newly crawled documents, wherein a respective document in the plurality of newly crawled document is associated with a query independent score; identifying (i) a newly crawled document in the plurality of newly crawled documents, and (ii) a first query independent score associated with the newly crawled document; and determining a first equivalence class, from among a plurality of equivalence classes, for the newly crawled document based upon a fingerprint for the newly crawled document, wherein the first equivalence class comprises a plurality of documents, each document in the plurality of documents is uniquely associated with a respective query independent score, and the fingerprint of the newly crawled document indicates that the newly crawled document is substantially identical to each document in the plurality of documents.
21. A method, comprising: at a computing device having one or more processors and memory: identifying a plurality of newly crawled documents, wherein a respective document in the plurality of newly crawled document is associated with a query independent score; identifying (i) a newly crawled document in the plurality of newly crawled documents, and (ii) a first query independent score associated with the newly crawled document; and determining a first equivalence class, from among a plurality of equivalence classes, for the newly crawled document based upon a fingerprint for the newly crawled document, wherein the first equivalence class comprises a plurality of documents, each document in the plurality of documents is uniquely associated with a respective query independent score, and the fingerprint of the newly crawled document indicates that the newly crawled document is substantially identical to each document in the plurality of documents. 22. The method of claim 21 , further comprising: determining which document in the plurality documents is to be included in a document index, wherein the document index is constrained to have a single document from the plurality of documents, wherein, when the newly crawled document is not in the document index, the newly crawled document is included in the index provided that the first query independent score exceeds by a threshold a query independent score of a document in the plurality of documents that is presently in the document index and when the newly crawled document is in the document index, the newly created document remains in the index provided that the first query independent score does not exceed by a threshold the largest query independent score associated with a document in the plurality of documents.