数据压缩的hash方法

DATA COMPRESSION WITH HASH CODES

在数据库应用中常要求数据压缩存贮。所采用的压缩方法应当有较小的系统开销和期望的压缩效果。文章给出了一种用其hash函数值作为编码来取代数据本身以减少文件的数据存贮量的压缩方法。该方法对许多应用都有较好的压缩效果,并其编码/解码的成本仅为对hash表一次查找或直接访问的开销。文章也讨论了hash编码数据压缩方法的实现技术,以及编码和解码的算法。

In many database applications, data have to be compressed before they can be stored. Data compression techniques with less overhead and better space saving are expected. This paper gives a data compression technique by which the size of a file may be reduced through substituting codes for its field values. The codes are the corresponding locations of the values in the hash table that is comprised of all the values of the field.The compression is effective for many applications, and the cost of the coding/decoding is equal to that of one access to the hash table. The implementation of the technique as a compression tool in DBMS for date storage and the algorithms of the coding/decoding are discussed.