presto-main/src/main/java/io/prestosql/type/DecimalOperators.java/DecimalOperators/negate
class DecimalOperators:        @LiteralParameters({"p", "s"})
        @SqlType("decimal(p, s)")
        public static Slice negate(@SqlType("decimal(p, s)") Slice arg)
        {
            BigInteger argBigInteger = Decimals.decodeUnscaledValue(arg);
            return encodeUnscaledValue(argBigInteger.negate());
        }