Importance

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Abstract

A B+ tree index for a full-text search through documents is created fast and fast searches are implemented using the index. A B+ tree index to register sets of words serving as keys and documents containing the words is constituted of a plurality of B+ tree subindexes; a document identification number id and a word identification number iw are assigned to a document and a word to uniquely identify them; as a function to apply to documents, a hash function Hd is provided that maps a document identification number to a value indicating the position of horizontal direction of a two-dimensional array, and as a function to apply to words, a hash function Hw is provided that maps a word identification number to a value indicating the position of vertical direction of the two-dimensional array; and the occurrence of a word in a document is registered in a corresponding subindex B+ tree (Hd(id), Hw(iw)) by using values obtained by applying the hash functions to the document identification number and the word identification number, respectively. The index is searched using a value with a word identification number as a key and a document identification number concatenated.

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First Claim