Key-sequential access methods for very large files derived from linear hashing

A novel class of order-preserving dynamic hashing structures is introduced and analyzed. The access method is referred to as dynamic random-sequential access method (DRSAM) and is derived from linear hashing. With respect to previous methods DRSAM presents the following characteristics: (1) the structure captures the hashed order in consecutive storage areas so that order-preserving schemes result in performance improvements for range queries and sequential processing; and (2) it adapts elastic buckets for the control of file growth. This approach outperforms the partial expansion method. The file structure is also extended with proper control mechanisms to cope with nonuniform distributions. The outcome is a multilevel trie stored as a two-level sequentially allocated file