Adaptive hashing with signatures

Adaptive hashing with signatures combines the adaptive hashing file structure together with superimposed signatures and several new algorithms to produce a new order-preserving data structure. This new technique has excellent direct retrieval performance, localized index organizations, and improved file index balance. In keeping with the principle advantage of the original adaptive hashing technique, algorithms to improve both primary and secondary memory storage utilization are also discussed. Furthermore, the new data structure has a high degree of flexibility, allowing it to be tailored for the optimum performance versus storage utilization ratio for a given application. Section 1: Introduction Several papers in the literature combine the idea of record signatures with dynamic file hashing methods to improve the performance of these data structures. In [1], Larson describes a technique using signatures and separators with linear hashing which guarantees retrieval of a record in a single probe. The use of signatures and separators is described in [2] and [3] and is referred to as signature hashing in [4]. A similar idea using signature hashing with dynamic hashing is presented in both [5] and [6]. Work in the general area of using signatures to improve retrieval performance continues, as in [7] which discusses an optimum distribution of signatures for signature hashing methods in general. Hsiao and Tharp’s original adaptive hashing data structure and algorithms are presented in [8]. Adaptive hashing was introduced as an alternative data structure to order-preserving linear hashing (OPLH) [9] and the B+-tree [10]. A comparison of the advantages and disadvantages of adaptive hashing, bounded disorder, and B+-trees can be found in [11]. All of these data structures share the property that both sequential and direct access of data records can be performed in an efficient manner. Adaptive hashing's main advantage over the B+-tree is that it requires less primary