Alternating hashing for expansible files

Abstract

In this paper, we propose a generalized approach for designing a class of dynamic hashing schemes which require no index and have the growth of a file at a rate of n+1/n per full expansion, where n is the number of pages of the file, as compared to a rate of two in linear hashing. Based on this generalized approach, we derive a new dynamic hashing scheme called alternating hashing, in which, when a split occurs in page k, the data records in page k will be redistributed to page k and page (k + 1), or page k and page (k - 1), according to whether the value of level dis even or odd, respectively. (Note that a level is defined as the number of full expansions happened so far.) From our performance analysis, given a fixed load control, the proposed scheme can achieve nearly 97% storage utilization as compared to 78% storage utilization by using linear hashing.