6. A system for detecting duplicated documents, comprising: one or more processors; memory storing one or more programs executable by the one or more processors, the one or more programs comprising instructions to: receive documents from one or more databases of documents, wherein each received document is associated with a respective query independent score; obtain a document content identifier for each received document, each document content identifier comprising an identifier of a respective document's content; index at least a subset of the received documents to produce an document index that maps terms to documents in the one or more databases of documents; and while performing the indexing, identify respective sets of received documents having the same content identifier, select a single document in each respective set of documents, in accordance with the query independent scores associated with the documents in the respective set of documents, as a representative document for the respective set of received documents, index the representative document, and with respect to each respective set of received documents, include only the representative document in the document index.
6. A system for detecting duplicated documents, comprising: one or more processors; memory storing one or more programs executable by the one or more processors, the one or more programs comprising instructions to: receive documents from one or more databases of documents, wherein each received document is associated with a respective query independent score; obtain a document content identifier for each received document, each document content identifier comprising an identifier of a respective document's content; index at least a subset of the received documents to produce an document index that maps terms to documents in the one or more databases of documents; and while performing the indexing, identify respective sets of received documents having the same content identifier, select a single document in each respective set of documents, in accordance with the query independent scores associated with the documents in the respective set of documents, as a representative document for the respective set of received documents, index the representative document, and with respect to each respective set of received documents, include only the representative document in the document index. 7. The system of claim 6 , wherein the document content identifier for a respective document comprises a fixed length fingerprint of document content of the respective document.