Linear Spiral Hashing for Expansible Files

• Authors: Ye-In Chang;Chien-I. Lee;Wann-Bay ChangLiaw
• Venue: IEEE Transactions on Knowledge and Data Engineering
• Year: 1999

The goal of dynamic hashing is to design a function and a file structure that allow the address space allocated to the file to be increased and reduced without reorganizing the whole file. In this paper, we propose a new scheme for dynamic hashing in which the growth of a file occurs at a rate of $\frac{n+k}{n}$ per full expansion, where $n$ is the number of pages of the file and $k$ is a given integer constant which is smaller than $n$, as compared to a rate of two in linear hashing. Like linear hashing, the proposed scheme (called linear spiral hashing) requires no index; however, the proposed scheme may or may not add one more physical page, instead of always adding one more page in linear hashing, when a split occurs. Therefore, linear spiral hashing can maintain a more stable performance through the file expansions and have much better storage utilization than linear hashing. From our performance analysis, linear spiral hashing can achieve nearly 97 percent storage utilization as compared to 78 percent storage utilization by using linear hashing, which is also verified by a simulation study.