Method, system, and device for evaluating performance of document search

Degradation in performance of document search is automatically detected. When document data is added to a database, a learning unit updates a language model by machine learning. A performance evaluation unit respectively calculates a first statistical value and a second statistical value related to ranking of each of a plurality of specific document data from a result of the document search using each of a plurality of first labels and second labels attached to a plurality of specific document data as a search query. The performance evaluation unit detects the degradation in performance of the document search when a variation value of the first statistical value due to update of a language model accompanying addition of at least one piece of document data is larger than a first threshold, and when a variation value of the second statistical value due to update is larger than a second threshold.