Class DoubleRollupUniqueOperator

All Implemented Interfaces:

public class DoubleRollupUniqueOperator extends Object implements IterativeChunkedAggregationOperator
This operator computes the single unique value of a particular aggregated state. If there are no values at all the 'no value key' is used. If there are more than one values for the state, the 'non unique key' is used. it is intended to be used at the second, and higher levels of rollup.