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公开(公告)号:US20040260675A1
公开(公告)日:2004-12-23
申请号:US10465148
申请日:2003-06-19
IPC分类号: G06F017/30
CPC分类号: G06F17/30469 , G06F17/30333 , Y10S707/962 , Y10S707/99935 , Y10S707/99936 , Y10S707/99937
摘要: A method of estimating cardinality of a join of tables using multi-column density values and additionally using coarser density values of a subset of the multi-column density attributes. In one embodiment, the subset of attributes for the coarser densities is a prefix of the set of multi-column density attributes. A number of tuples from each table that participate in the join may be estimated using densities of the subsets. The cardinality of the join can be estimated using the multi-column density for each table and the estimated number of tuples that participate in the join from each table.
摘要翻译: 使用多列密度值估计表连接的基数的方法,并且另外使用多列密度属性的子集的较粗密度值。 在一个实施例中,用于较粗密度的属性子集是多列密度属性集合的前缀。 可以使用子集的密度来估计参与加入的每个表中的一些元组。 可以使用每个表的多列密度和参与每个表的连接的元组的估计数量来估计连接的基数。