Retrieval control method, and retrieval control device

A retrieval control method by a computer, comprising:

• receiving a retrieval request including range information that designates a retrieval range of the retrieval request;
• specifying a total number of records included in the retrieval range designated by the range information, and estimating the number of records to be obtained by performing retrieval in the retrieval range, by utilizing a correspondence relation information stored in a storage unit, the correspondence relation information including relationships between the retrieval range and the total number of records included in the retrieval range;
• calculating a difference between a cost of retrieval processing time and a cost of retrieval processing time, the cost of retrieval processing time being calculated on a condition when retrieval processing is performed by a first process or thread which performs the retrieval processing for a record of the total number of records, and the cost of retrieval processing time being calculated on a condition when retrieval processing is performed by parallel retrieval using a plurality of processes or threads controlled by the first process or thread;
• calculating a cost of time for giving a record of the estimated number of records from the plurality of processes or threads to the first process or thread;
• and
• controlling, according to a comparison result between the difference and the calculated cost of the time, whether the retrieval request is to be processed by the parallel retrieval.

A retrieval control device comprising:

• a communication unit configured to receive a retrieval request including range information that designates a retrieval range of the retrieval request;
• an estimation unit configured to specify a total number of records included in the retrieval range designated by the range information, and to estimate the number of records to be obtained by performing retrieval in the retrieval range, by utilizing a correspondence relation information stored in a storage unit, the correspondence relation information including relationships between the retrieval range and the total number of records included in the retrieval range;
• a first calculation unit configured to calculate a difference between a cost of retrieval processing time and a cost of retrieval processing time, the cost of retrieval processing time being calculated on a condition when retrieval processing is performed by a first process or thread which performs the retrieval processing for a record of the total number of records, and the cost of retrieval processing time being calculated on a condition when retrieval processing is performed by parallel retrieval using a plurality of processes or threads controlled by the first process or thread;
• a second calculation unit configured to calculate a cost of time for giving a record of the estimated number of records from the plurality of processes or threads to the first process or thread;
• and
• a determination unit configured to control, according to a comparison result between the difference and the calculated cost of the time, whether the retrieval request is to be processed by the parallel retrieval.