| 摘要 |
A retrieval apparatus 100 for searching document data comprises a document storage area 141 for storing documents to be searched and a document management table 142 for storing a data size of a document such that the data size is associated with a document ID for identifying the document. The retrieval apparatus 100 reads 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 t 1 taken for a retrieval process by the index scan method and an estimated time t 2 taken for the retrieval process by the text scan method, based on the retrieval document size. The retrieval apparatus 100 compares the estimated times t 1 and t 2 , and decides which method to use for a retrieval process, the index scan method or the text scan method.
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