Patent ID: 7702666

Claim:
A database management system managing a database, the system comprising: a first data retaining part for performing a search operation of data at a first speed using a stored inverted list of a first full-text index, and for performing a changing operation of data at a second speed slower than the first speed, wherein the changing operation comprises an insertion operation, an updating operation, or a deletion operation; three or more second data retaining parts, each second data retaining part performing a changing operation of data and a search operation of data using a stored inverted list of a second full-text index, wherein said changing operation of data is performed at a higher speed than said search operation of data, and at least one of the second data retaining parts conducts a deletion operation as the only changing operation; a data transfer part for obtaining a stored inverted list of a second full-text index and transferring data from the stored inverted list of the second full-text index to the stored inverted list of the first full-text index so as to reflect a result of the changing operation; a database operation request processing part for executing an operation request with respect to the database; a transaction processing part for guaranteeing a consistency of data between said data transfer part and said database operation request processing part; a file switching part for switching said second data retaining parts based on the operation request with respect to the database and an asynchronous merge processing to said first data retaining part so that when one of said second data retaining parts is used for the asynchronous merge processing, a different second data retaining part is used for the operation request with respect to the database; and a data amount judging part for judging whether or not an amount of data in one of the second data retaining parts used for the operation request with respect to the database exceeds a threshold value, wherein said file switching part switches one of said second data retaining parts judged by said data amount judging part to exceed said threshold value for the merge processing, and switches another unused second data retaining part for the second data retaining part used for the operation request with respect to the database.