presto-main/src/main/java/io/prestosql/operator/aggregation/ApproximateCountDistinctAggregation.java/ApproximateCountDistinctAggregation/evaluateFinal
class ApproximateCountDistinctAggregation:    @OutputFunction(StandardTypes.BIGINT)
    public static void evaluateFinal(BooleanDistinctState state, BlockBuilder out)
    {
        BIGINT.writeLong(out, Integer.bitCount(state.getByte()));
    }