Patent ID: 7797324
Filing Date: 2010-09-14
Classification: G06F

Abstract:
1. A document retrieval system performing retrieval of electronic documents, comprising: a document database storing a plurality of pieces of document data, to each of which a document number is attached; a transposed index storage device storing a transposed index in which the document numbers of the document data containing a keyword string are registered as an array in ascending order of numerical value of the document number by mapping to each of a plurality of the keyword strings; a document number subsequence search start address table storage device storing a document number subsequence search start address table in which a value obtained by dividing a total number of documents, which is a number of pieces of document data registered with the document database, by a number of units planned for parallel operation is set as a number of assigned documents per unit, document groups obtained by compiling the document data in the document database into sets, each of which has as many documents as the number of assigned documents in ascending order of the document number, are sequentially defined as assigned document groups, the value of the document number corresponding to start document data in each of the defined assigned document groups is set as an assigned document group start document number of each, and a subsequence search start address indicating a position where the assigned document group start document number is recorded in an array of the document numbers mapped to each of the keyword strings in the transposed index is registered by mapping to the keyword string in ascending order of value of the corresponding assigned document group start document number; a document retrieval managing unit having document number subsequence acquisition request means for transmitting the total number of documents, a number of units in parallel processing indicating a number of document number subsequence acquisition apparatuses in operation, and a document number subsequence acquisition request containing a retrieval keyword to each of a plurality of the document number subsequence acquisition apparatuses in response to a document retrieval request containing the retrieval keyword from a retrieval request apparatus, document number array summarization means for generating a document number array by acquiring document number subsequences returned from a plurality of the document number subsequence acquisition apparatuses in accordance with the document number subsequence acquisition request and summarizing the document numbers contained in the document number subsequences, document list creation means for creating a document list for the extracted document data after extracting the document data corresponding to each of the document numbers contained in the document number array generated by the document number array summarization means from the document database, and retrieval result notification means for transmitting the document list created by the document list creation means to the retrieval request apparatus; and a plurality of the document number subsequence acquisition apparatuses having assigned document group determination means for determining a document group in a sequence in accordance with a preset apparatus number of a local apparatus as the assigned document group when, upon receipt of the document number subsequence acquisition request from the document retrieval managing unit, the number of assigned documents per unit is calculated by dividing the total number of documents by the number of units in parallel processing and document groups obtained by compiling the document data in the document database into sets, each of which has as many documents as the number of assigned documents in ascending order of the document number, are sequentially defined, subsequence search start position determination means for extracting the subsequence search start address corresponding to the assigned document group start document number registered in the sequence in accordance with the apparatus number of the local apparatus from a plurality of the subsequence search start addresses associated with the keyword string corresponding to the retrieval keyword by referencing the document number subsequence search start address table in the document number subsequence search start address table storage device, and subsequence acquisition means for referencing the transposed index in the transposed index storage device, searching the array of the document numbers from the position indicated by the subsequence search start address extracted by the subsequence search start position determination means in ascending order, acquiring the document numbers contained in the assigned document group in the document number array associated with the keyword string corresponding to the retrieval keyword, and transmitting a set of the acquired document numbers to the document retrieval managing unit as the document number subsequence.