cassandra/cqlengine/functions.py

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from datetime import datetime

from cassandra.cqlengine import UnicodeMixin, ValidationError

def get_total_seconds(td):
    return td.total_seconds()

class QueryValue(UnicodeMixin):
    """
    Base class for query filter values. Subclasses of these classes can
    be passed into .filter() keyword args
    """

    format_string = '%({0})s'

    def __init__(self, value):
        self.value = value
        self.context_id = None

    def __unicode__(self):
        return self.format_string.format(self.context_id)

    def set_context_id(self, ctx_id):
        self.context_id = ctx_id

    def get_context_size(self):
        return 1

    def update_context(self, ctx):
        ctx[str(self.context_id)] = self.value


class BaseQueryFunction(QueryValue):
    """
    Base class for filtering functions. Subclasses of these classes can
    be passed into .filter() and will be translated into CQL functions in
    the resulting query
    """
    pass


class TimeUUIDQueryFunction(BaseQueryFunction):

    def __init__(self, value):
        """
        :param value: the time to create bounding time uuid from
        :type value: datetime
        """
        if not isinstance(value, datetime):
            raise ValidationError('datetime instance is required')
        super(TimeUUIDQueryFunction, self).__init__(value)

    def to_database(self, val):
        epoch = datetime(1970, 1, 1, tzinfo=val.tzinfo)
        offset = get_total_seconds(epoch.tzinfo.utcoffset(epoch)) if epoch.tzinfo else 0
        return int((get_total_seconds(val - epoch) - offset) * 1000)

    def update_context(self, ctx):
        ctx[str(self.context_id)] = self.to_database(self.value)


class MinTimeUUID(TimeUUIDQueryFunction):
    """
    return a fake timeuuid corresponding to the smallest possible timeuuid for the given timestamp

    http://cassandra.apache.org/doc/cql3/CQL-3.0.html#timeuuidFun
    """
    format_string = 'MinTimeUUID(%({0})s)'


class MaxTimeUUID(TimeUUIDQueryFunction):
    """
    return a fake timeuuid corresponding to the largest possible timeuuid for the given timestamp

    http://cassandra.apache.org/doc/cql3/CQL-3.0.html#timeuuidFun
    """
    format_string = 'MaxTimeUUID(%({0})s)'


class Token(BaseQueryFunction):
    """
    compute the token for a given partition key

    http://cassandra.apache.org/doc/cql3/CQL-3.0.html#tokenFun
    """
    def __init__(self, *values):
        if len(values) == 1 and isinstance(values[0], (list, tuple)):
            values = values[0]
        super(Token, self).__init__(values)
        self._columns = None

    def set_columns(self, columns):
        self._columns = columns

    def get_context_size(self):
        return len(self.value)

    def __unicode__(self):
        token_args = ', '.join('%({0})s'.format(self.context_id + i) for i in range(self.get_context_size()))
        return "token({0})".format(token_args)

    def update_context(self, ctx):
        for i, (col, val) in enumerate(zip(self._columns, self.value)):
            ctx[str(self.context_id + i)] = col.to_database(val)