System, method, and apparatus for searching information across distributed databases

A searching method in a searching system that includes a plurality of information managing apparatuses, and a searching apparatus that searches for information across the information managing apparatuses, the plurality of information managing apparatuses and the searching apparatus being connected to one another by way of a network, each of the information managing apparatuses managing one of a plurality of databases, the plurality of databases storing the information in a distributed manner, the information including at least one item, the searching method comprising:

• storing by the searching apparatus in a locality storing unit, a data attribute of the item, a type of a condition that the item should meet, and locality information in association with one another, the locality information indicating whether the item is distributed across the databases;
• receiving a search request including the condition by the searching apparatus;
• analyzing the received search request by the searching apparatus;
• generating by the searching apparatus a search plan including a request of creating a logical sequence by merging pieces of sequence information and a plurality of requests of obtaining one of the pieces of the sequence information, each piece of the sequence information including the item in a list structure;
• obtaining by the searching apparatus from the locality storing unit the locality information that corresponds to the data attribute of the item included in the each piece if the sequence information and the type of the condition that the item included in the each piece of the sequence information should meet;
• determining by the searching apparatus whether the item included in the each piece of the sequence information is distributed across the databases in accordance with the obtained locality information;
• removing by the searching apparatus the request of creating the logical sequence from the search plan and thereby updating the search plan when the searching apparatus determines that the item is not distributed across the databases;
• sending an execution request of the updated search plan to the information managing apparatuses by the searching apparatus;
• receiving the execution request from the searching apparatus by the information managing apparatuses;
• and
• executing the search plan in accordance with the received execution request by the information managing apparatuses.

A searching apparatus that is connected to a plurality of information managing apparatuses by way of a network, each of the information managing apparatuses managing one of a plurality of databases, the plurality of databases storing information in a distributed manner, each of the information including at least one item, the searching apparatus comprising:

• a search request receiving unit that receives a search request including a condition that the item should meet;
• a locality storing unit that stores a data attribute of the item, stores a type of the condition, and stores locality information in association with one another, the locality information indicating whether the item is distributed across the databases;
• a plan generating unit that analyzes the search request received by the search request receiving unit, and generates a search plan including a request of creating a logical sequence by merging pieces of sequence information and a plurality of requests of obtaining one of the pieces of the sequence information, each piece of the sequence information including the item in a list structure;
• a determining unit that obtains from the locality storing unit the locality information that corresponds to the data attribute of the item included in the each piece of the sequence information and the type of the condition that the item included in the each piece of the sequence information should meet, and determines whether the item included in the each piece of the sequence information is distributed across the databases in accordance with the obtained locality information;
• an updating unit that removes the request of creating the logical sequence from the search plan and thereby updates the search plan, when the determining unit determines that the item is not distributed across the databases;
• and
• an execution requesting unit that sends an execution request of the search plan updated by the updating unit to the information managing apparatuses.