Variable Hashing for Temporal Data
时态数据的可变Hash索引

Index technology is one of the important factors during the process of data query optimizing,especially for temporal database.A new hashing method for temporal data is designed to improve the efficiency of database snapshot query in this paper,and the method is called Variable Hashing (VH).Generally,it's difficult to establish hashing in- dex for time value because of the time's indeterminacy.VH solves this problem,and it is based on the start time of a database's transaction time attribute.The parameters of hashing function are variableaccording to the time attribute of tuples,and they are organized as a B~+-tree.Using a time value to query the B~+-tree can get the hashing parameters, and the parameters can be used to calculate the address of target data.Carefull analysis and experimental test show that the time complexity of VH's snapshot query is better than other snapshot index methods,and its space complexity is also optimal.