presto-main/src/main/java/io/prestosql/operator/scalar/MathFunctions.java/MathFunctions/roundLongLong
class MathFunctions:        @LiteralParameters({"p", "s", "rp", "rs"})
        @SqlType("decimal(rp, rs)")
        @Constraint(variable = "rp", expression = "min(38, p - s + min(1, s))")
        @Constraint(variable = "rs", expression = "0")
        public static Slice roundLongLong(@LiteralParameter("s") long numScale, @SqlType("decimal(p, s)") Slice num)
        {
            if (numScale == 0) {
                return num;
            }
            return rescale(num, -(int) numScale);
        }