Estimation of column cardinality in a partitioned relational database

摘要

The present invention is directed to a system, method and computer readable medium for estimating a column cardinality value for a column in a partitioned table stored in a plurality of nodes in a relational database. According to one embodiment of the present invention, a plurality of column values for the partitioned table stored in each node are hashed, and a hash data set for each node is generated. Each of the hash data sets from each node is transferred to a coordinator node designated from the plurality of nodes. The hash data sets are merged into a merged data set, and an estimated column cardinality value for the table is calculated from the merged data set.