METHODS AND APPARATUS FOR INFORMATION STORAGE AND RETRIEVAL UTILIZING A METHOD OF HASHING AND DIFFERENT COLLISION AVOIDANCE SCHEMES DEPENDING UPON CLUSTERING IN THE HASH TABLE

An apparatus for performing storage and retrieval in an information storage system is disclosed which uses the hashing technique. In order to provide efficient and graceful operation under varying loading conditions, the system shifts between collision avoidance by linear probing with open addressing when the load is below a threshold, and collision avoidance by external chaining when the load is above a threshold. Insertion, deletion and retrieval operations are arranged to switch dynamically between the two collision avoidance stratagems as the local loading factor on the system, as measured by the number of records hashed to the same address, crosses preselected thresholds.