presto-main/src/main/java/io/prestosql/operator/scalar/MathFunctions.java/MathFunctions/signDecimalShort
class MathFunctions:        @LiteralParameters({"p", "s"})
        @SqlType("decimal(1,0)")
        public static long signDecimalShort(@SqlType("decimal(p, s)") long num)
        {
            return (long) Math.signum(num);
        }