Amazon Redshift announces support for HyperLogLog Sketches
Amazon Redshift introduces support for natively storing and processing HyperLogLog (HLL) sketches. HyperLogLog is a novel algorithm that efficiently estimates the approximate number of distinct values in a data set. HLL sketch is a construct that encapsulates the information about the distinct values in the data set. You can use HLL sketches to achieve significant performance benefits for queries that compute approximate cardinality over large data sets, with an average relative error between 0.01–0.6%.
Source:: Amazon AWS