1. A system for creating an index for a document collection, the system comprising: at least one processor; and a computer readable storage medium storing instructions that, when executed by the processor, causes the processor to: compare a keyword in one or more documents to a plurality of noisy keywords associated with a document collection; determine whether the keyword is a noisy keyword; determine, for one of the documents, a keyword position and a number of noisy keywords preceding the keyword; create, for the one of the documents, a token including a document identifier, an indication whether the keyword is a noisy keyword, the keyword position, and the number of noisy keywords preceding the keyword; and store the token in an index.