Saturday, 18 April 2015

Hyperloglog commands

HyperLogLog is a data structure that is used to count number of distinct elements in a set approximately. Calculating the exact number of elements in a set requires an amount of memory proportional to the number of elements, which is impractical for very large data sets. Probabilistic cardinality estimators, such as the HyperLogLog data structure, use significantly less memory than this, at the cost of obtaining only an approximation of the cardinality.
      Adds all elements to hyperLogLog data structure
       Returns the approximated cardinality computed by the HyperLogLog data structure
      Merge multiple HyperLogLog(sourcekey1 sourcekey2 ... sourcekeyN) values into an unique value


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