Hitachi, Ltd.

Tsuyoshi Sudo

Kazutomo Ushijima

Tadataka Matsubayashi

Kentaro Chigusa

A retrieval apparatusfor searching document data comprises a document storage areafor storing documents to be searched and a document management tablefor storing a data size of a document such that the data size is associated with a document ID for identifying the document. The retrieval apparatusreads out from the document management table data sizes of documents to be searched, and calculates a retrieval document size by adding up the read out data sizes, and calculates an estimated time ttaken for a retrieval process by the index scan method and an estimated time ttaken for the retrieval process by the text scan method, based on the retrieval document size. The retrieval apparatuscompares the estimated times tand t, and decides which method to use for a retrieval process, the index scan method or the text scan method.

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Ichikawa, Japan

Tsuyoshi Sudo