Partial expansions for file organizations with an index

Abstract

A new way to increase file space in dynamically growing files is introduced in which substantial improvement in file utilization can be achieved. It makes use of partial expansions in which, instead of doubling the space associated with some part of the file, the space grows at a slower rate. Unlike previous versions of partial expansion in which the number of buckets involved in file growth is increased by less than a factor of two, the new method expands file space by increasing bucket size via “elastic buckets.” This permits partial expansions to be used with a wide range of indexed files, including B-trees. The results of using partial expansions are analyzed, and the analysis confirmed by a simulation study. The analysis and simulation demonstrate that the file utilization gains are substantial and that fears of excessive insertion cost resulting from more frequent file growth are unfounded.