presto-spi/src/main/java/io/prestosql/spi/type/DecimalType.java/DecimalType/DecimalType
class DecimalType:    DecimalType(int precision, int scale, Class<?> javaType)
    {
        super(new TypeSignature(StandardTypes.DECIMAL, buildTypeParameters(precision, scale)), javaType);
        this.precision = precision;
        this.scale = scale;
    }