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Method for Extendible Hashing

IP.com Disclosure Number: IPCOM000070038D
Original Publication Date: 1978-Jul-01
Included in the Prior Art Database: 2005-Feb-21

Publishing Venue

IBM

Related People

Authors:
Fagin, R Pippenger, NJ Strong, HR [+details]

Abstract

This article describes a method for expanding the content of hash tables dynamically as the size of the underlying data base increases. The method starts with the use of a key (or unique identifier) K, either of fixed or variable length. In this method, it is necessary to locate the data associated with K for the purpose of insertion, deletion, or update. Let there exist a fixed hash f, selected from a class of "universal hash functions." There is defined a pseudokey K' associated with K by the expression K'=f(K). The function f should be selected such that the pseudokeys are of fixed length and distributed nearly uniformly. As an example, one half of the pseudokeys have a final bit of zero, while one quarter of the pseudokeys end with bits 01, etc.