| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an N-gram index and a compressed full-text indexing hybrid index.SOLUTION: A search server of a document retrieval device executes, as document retrieval processing means, an N-gram indexed search with regard to an index term corresponding to each search term in a search expression, and calculates a predicted value of processing time for the search term by compressed full-text indexing by using information about the index term in an N-gram index database. The search server constructs, on the basis of the predicted value, a compressed full-text indexed search expression in which the sequence of processing of the search term by compressed full-text indexing is changed, skips a search when a search by compressed full-text indexing for the search term included in the constructed search expression is unnecessary, acquires information about the index term constituting the search term from the N-gram index database to reduce the number of times characters are collated by compressed full-text indexing, and executes a compressed full-text indexed search on a compressed full-text indexing database by using the compressed full-text indexed search expression.</p> |
