public static <Key, Value> Aggregation<Key, Long, Long> longSum() {
        return new AggregationAdapter(new LongSumAggregation<Key, Value>());
    }
public static < Key , Value > Aggregation < Key , Long , Long > longSum ( ) { return new AggregationAdapter ( new LongSumAggregation < Key , Value > ( ) ) ; }
Returns an aggregation to calculate the long sum of all supplied values.<br/>
This aggregation is similar to: <pre>SELECT SUM(value) FROM x</pre>

@param <Key>   the input key type
@param <Value> the supplied value type
@return the sum over all supplied values