presto-main/src/main/java/io/prestosql/operator/scalar/MathFunctions.java/MathFunctions/absLong
class MathFunctions:        @LiteralParameters({"p", "s"})
        @SqlType("decimal(p, s)")
        public static Slice absLong(@SqlType("decimal(p, s)") Slice arg)
        {
            if (isNegative(arg)) {
                Slice result = unscaledDecimal(arg);
                negate(result);
                return result;
            }
            else {
                return arg;
            }
        }