A method of counting unique items in a database system

摘要

A method of counting items in a database system having one or more nodes comprising one or more processors and memory, the memory of the one or more nodes storing one or more programs to be executed by the one or more processors.
An M number of items is identified and the unique items of the M number of items are counted by determining a logcount for the unique items of the M number of items which is then stored. To determine a logcount partitioning each of the unique items of the M number of items are first partitioned into a set of N number of parts, wherein each N part includes a subset of the unique items of the M number of items and wherein each subset of unique items is expressed as a bit value. The lowest unset bit in each of the N number of parts for each subset of the M number of items is then found and the lowest bit in N intermediate values for each subset of unique items in the set of N parts is set. By averaging the lowest unset bit values of the N intermediate values for each set of N parts, the averaged value as a log value expressed in powers-of two is determined.