Patent ID: 7966307
Filing Date: 2011-06-21
Classification: G06F

Abstract:
1. A document search method with which a document search apparatus searches for a document from a document database (DB) in response to an input of a search query consisting of keywords that are combined using a logical formula, the document search apparatus including: a central processing unit (CPU); the document DB storing documents to be searched; and an index DB storing an index term included in the documents to be searched, the number of documents including the index term, and a document list of documents including the index term, the method comprising causing the document search apparatus to execute the steps of: constructing a search query for an index-type search, by replacing each keyword included in the inputted search query with conjunctions of index terms constituting the keyword; calculating a sum of a time required for an index-type search and a time required for a scan-type search, the sum representing an estimated value of a total search time required for the index-type search and scan-type search; wherein the time required for the index-type search and the number of documents to be searched are estimated for each term in the search query for an index-type search, the estimate being made by regarding, as hitting all the documents, another term having a larger number of hits than the each term in reference to the document index DB; and wherein the time required for the scan-type search, in which the estimated number of documents are scanned by using the inputted search query, is estimated; constructing a search query for an index-type search by replacing, with a logical TRUE, a term which is regarded as hitting all documents when the estimated total search time takes the minimum value; performing an index-type search using the search query for an index-type search including the logical TRUE; performing a scan-type search on a document, which is searched by the index-type search, by using the inputted search query; and outputting a document that is returned by the scan-type search.