| 摘要 |
PURPOSE:To abbreviate a retrieval means and to attain high speed indexing by collating an index retrieval history at the time of subsequent retrieving of index and using it if there is reavailable one. CONSTITUTION:An index retrieval means 3 takes out an index key value among index retrieval requests by an index key value collating part 21, calls a history response part 22, and calls a history control means 4 with the received index key value as a parameter so as to permit it to check whether there is any reavailable index retrieval history. If there is, it is received from the history control means 4, is moved, and stored, whereby a retrieval procedure from a most significant level index block 27 is abbreviated.
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