class TimeStamp(sa_types.TypeDecorator):
    """Represents datetime/time timestamp object as a bigint value.

    Despite the fact that timestamp objects are represented by float value in
    python, the Float column cannot be used for storing such values, since
    timestamps values can be bigger than the limit of Float columns at some
    back-ends (the value will be cropped in such case). Also, using DateTime
    type is not convenient too, since it do not accurate with microseconds.
    """

    impl = sa_types.BigInteger
    _coefficient = 1000000.0

    def process_bind_param(self, value, dialect):
        if value is None:
            return None
        return value * self._coefficient

    def process_result_value(self, value, dialect):
        if value is None:
            return None
        return value / self._coefficient

    def coerce_compared_value(self, op, value):
        if isinstance(value, int):
            return sa_types.BigInteger()
        else:
            return self