presto-main/src/main/java/io/prestosql/operator/aggregation/RealCorrelationAggregation.java/RealCorrelationAggregation/combine
class RealCorrelationAggregation:    @CombineFunction
    public static void combine(@AggregationState CorrelationState state, @AggregationState CorrelationState otherState)
    {
        DoubleCorrelationAggregation.combine(state, otherState);
    }