Application of Minimal Perfect Hashing in Main Memory Indexing

Abstract

With the rapid decrease in the cost of random access memory (RAM), it will soon become economically feasible to place full-text indexes of a library in main memory. One essential component of the indexing system is a hashing algorithm, which maps a keyword into the memory address of the index information corresponding to that keyword. This thesis studies the application of the minimal perfect hashing algorithm in main memory indexing. This algorithm is integrated into the index search engine of the Library 2000 system, a digital on-line library system. The performance if this algorithm is compared with that of the open-address hashing scheme. We find that although the minimal perfect hashing algorithm needs fewer keyword comparisons per keyword search on average, its hashing performance is slower than the open-addressing scheme.