Patent ID: 7478083
Filing Date: 2009-01-13
Classification: G06F,Y10S

Abstract:
1. A method for estimating a cardinality for a plurality of columns in a database system comprising: obtaining statistics for the plurality of columns, a first portion of the statistics indicating at least one relationship between at least a portion of the plurality of columns, a second portion of the statistics including single column statistics; and utilizing the first portion and the second portion of the statistics to estimate the cardinality for the plurality of columns, including: using column equivalency to determine which of the first portion and the second portion of the statistics to utilize in estimating the cardinality, including homogenizing the at least the second portion of the statistics if possible; and recursively calculating a key cardinality based upon the statistics, the key cardinality indicating the cardinality of the plurality of columns, the recursively calculating including: