presto-main/src/main/java/io/prestosql/operator/scalar/MathFunctions.java/MathFunctions/absSmallint
class MathFunctions:    @Description("absolute value")
    @ScalarFunction("abs")
    @SqlType(StandardTypes.SMALLINT)
    public static long absSmallint(@SqlType(StandardTypes.SMALLINT) long num)
    {
        checkCondition(num != Short.MIN_VALUE, NUMERIC_VALUE_OUT_OF_RANGE, "Value -32768 is out of range for abs(smallint)");
        return Math.abs(num);
    }