django/db/models/query_utils.py

   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