New order preserving access methods for very large files derivedfrom linear hashing

A class of order-preserving dynamic hashing structures is introduced and analyzed. The access method is referred to as the dynamic random-sequential access method (DRSAM) and is derived from linear hashing. A new logical to physical mapping that is based on sequential bucket allocations in hash order is proposed. With respect to previous methods, this allocation technique has the following characteristics: (1) the structure captures the hashed order in consecutive storage areas so that order preserving (OPH) schemes should result in performance improvements for range queries and sequential processing; and (2) it adapts elastic buckets for the control of file growth. Under specific conditions, this approach outperforms the partial expansion method previously proposed by P.-A. Larson (1982)