9. A system, comprising: at least one memory; and at least one processor, connected to the at least one memory, to: store re-crawl information indicating which document of a plurality of documents has been re-crawled, assign the documents to one or more clusters in a current clustering operation, select a current representative document for each of the one or more clusters, determine whether the current representative document has been re-crawled based on the re-crawl information, determine a previous representative document associated with the current representative document, if it is determined that the current representative document has not been re-crawled, combine together one of the one or more clusters associated with the current representative document that has not been re-crawled and one of the one or more clusters to which the previous representative document has been assigned in the current clustering operation, and store information related to each of the one or more clusters.
9. A system, comprising: at least one memory; and at least one processor, connected to the at least one memory, to: store re-crawl information indicating which document of a plurality of documents has been re-crawled, assign the documents to one or more clusters in a current clustering operation, select a current representative document for each of the one or more clusters, determine whether the current representative document has been re-crawled based on the re-crawl information, determine a previous representative document associated with the current representative document, if it is determined that the current representative document has not been re-crawled, combine together one of the one or more clusters associated with the current representative document that has not been re-crawled and one of the one or more clusters to which the previous representative document has been assigned in the current clustering operation, and store information related to each of the one or more clusters. 13. The system of claim 9 , where the one of the one or more clusters associated with the current representative document that has not been re-crawled includes another document in addition to the current representative document.