11. The system of claim 10 , wherein the inverted index querier is configured to query the inverted index with a plurality of batch queries, each batch query using a subset of the set of covering token sets to query the inverted index.
10. The system of claim 9 , wherein the document filter comprises: an inverted index querier configured to query an inverted index generated on the first set of documents using the set of covering token sets to determine a set of document identifiers for a subset of the documents in the first set; a document retriever configured to retrieve a subset of documents from the first set identified by the set of document identifiers; and an entity string matcher configured to perform entity string matching on the retrieved subset of documents.