9. A system for ad-hoc entity extraction, comprising: one or more processors; a document filter configured to filter a first set of documents to generate a second set of documents that includes documents of the first set based at least on a set of token sets that covers entity strings in a list of entity strings, the number of tokens in the set of token sets being less than the number of words of the entity strings in the list of entity strings, the set of tokens generated based on the entity strings in the list of the entity strings; and an entity recognition module configured to perform entity recognition on the second set of documents.
9. A system for ad-hoc entity extraction, comprising: one or more processors; a document filter configured to filter a first set of documents to generate a second set of documents that includes documents of the first set based at least on a set of token sets that covers entity strings in a list of entity strings, the number of tokens in the set of token sets being less than the number of words of the entity strings in the list of entity strings, the set of tokens generated based on the entity strings in the list of the entity strings; and an entity recognition module configured to perform entity recognition on the second set of documents. 14. The system of claim 9 , wherein the document filter is configured to filter the first set of documents to generate the second set of documents to include documents of the first set having at least a partial match with at least one entity string in the list of entity strings.