1 """

     2 Various data structures used in query construction.

     3 

     4 Factored out from django.db.models.query so that they can also be used by other

     5 modules without getting into circular import difficulties.

     6 """

     7 

     8 from copy import deepcopy

     9 

    10 from django.utils import tree

    11 

    12 class QueryWrapper(object):

    13     """

    14     A type that indicates the contents are an SQL fragment and the associate

    15     parameters. Can be used to pass opaque data to a where-clause, for example.

    16     """

    17     def __init__(self, sql, params):

    18         self.data = sql, params

    19 

    20 class Q(tree.Node):

    21     """

    22     Encapsulates filters as objects that can then be combined logically (using

    23     & and |).

    24     """

    25     # Connection types

    26     AND = 'AND'

    27     OR = 'OR'

    28     default = AND

    29 

    30     def __init__(self, *args, **kwargs):

    31         super(Q, self).__init__(children=list(args) + kwargs.items())

    32 

    33     def _combine(self, other, conn):

    34         if not isinstance(other, Q):

    35             raise TypeError(other)

    36         obj = deepcopy(self)

    37         obj.add(other, conn)

    38         return obj

    39 

    40     def __or__(self, other):

    41         return self._combine(other, self.OR)

    42 

    43     def __and__(self, other):

    44         return self._combine(other, self.AND)

    45 

    46     def __invert__(self):

    47         obj = deepcopy(self)

    48         obj.negate()

    49         return obj

    50