| 摘要 |
PROBLEM TO BE SOLVED: To minimize the length of a retrieved result information storing area by selecting a method for minimizing the length of a retrieved result position information area in each retrieving processing out of two methods. SOLUTION: Each bit of a retrieved result bit map 202 corresponds to a line ID to be positional information in a data base for real data as a pair. When real data pointed out by a line ID corresponding to each bit satisfy the retrieving condition of an entry pointing out its bit map, '1' is set up in the bit, and when the retrieving condition is not satisfied, '0' is set up. In a retrieved result line ID list 203, the line ID of real data satisfying the retrieving condition of an entry pointing out the list is expressed by a list format. Which is used for preparing retrieved result position information, the bit map 202 or the list 203, is determined by calculating necessary area length from the hit ratio of retrieval. The bit map 202 has area length proportional to the number of table data to be retrieved and the list 203 reduces its necessary area length in proportion to the reduction of a hit ratio.
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