摘要：

在概率关系中，聚集查询的目标是每一个可能世界，而可能世界的数目随着概率关系元组数目的增长呈指数增长，当元组数目较多时，聚集查询在线性时间内无法计算。针对该问题，分别为每一个聚集函数定义3个聚集分量，通过对原概率关系进行编码，分别采用转换、存储过程和近似计算的方法，在线性时间内实现聚集查询，理论证明和实验结果表明该方法的正确性和有效性。

关键词: 聚集查询, 聚集函数, 近似计算

Abstract:

In probabilistic database, aggregation query processes each possible world, but the number of possible may be exponentially growing with the increase of tuple number. So, aggregation query can not be calculated in linear time when there is a relatively large number of tuples. Three aggregation components are defined for each aggregation function. By encoding original probabilistic relation and using conversion, storage procedure and approximate calculation methods respectively, aggregation query can be implemented in linear time. Theoretical proof and experimental results show that the methodology used is correct and efficient.

Key words: aggregation query, aggregation function, approximation computation

中图分类号: 

• TP311