1 files changed, 67 insertions, 0 deletions
diff --git a/webapp/django/db/models/query_utils.py b/webapp/django/db/models/query_utils.py
new file mode 100644
index 0000000000..8dbb1ec667
--- /dev/null
+++ b/webapp/django/db/models/query_utils.py
@@ -0,0 +1,67 @@
+"""
+Various data structures used in query construction.
+
+Factored out from django.db.models.query so that they can also be used by other
+modules without getting into circular import difficulties.
+"""
+
+from copy import deepcopy
+
+from django.utils import tree
+
+class QueryWrapper(object):
+    """
+    A type that indicates the contents are an SQL fragment and the associate
+    parameters. Can be used to pass opaque data to a where-clause, for example.
+    """
+    def __init__(self, sql, params):
+        self.data = sql, params
+
+class Q(tree.Node):
+    """
+    Encapsulates filters as objects that can then be combined logically (using
+    & and |).
+    """
+    # Connection types
+    AND = 'AND'
+    OR = 'OR'
+    default = AND
+
+    def __init__(self, *args, **kwargs):
+        super(Q, self).__init__(children=list(args) + kwargs.items())
+
+    def _combine(self, other, conn):
+        if not isinstance(other, Q):
+            raise TypeError(other)
+        obj = deepcopy(self)
+        obj.add(other, conn)
+        return obj
+
+    def __or__(self, other):
+        return self._combine(other, self.OR)
+
+    def __and__(self, other):
+        return self._combine(other, self.AND)
+
+    def __invert__(self):
+        obj = deepcopy(self)
+        obj.negate()
+        return obj
+
+def select_related_descend(field, restricted, requested):
+    """
+    Returns True if this field should be used to descend deeper for
+    select_related() purposes. Used by both the query construction code
+    (sql.query.fill_related_selections()) and the model instance creation code
+    (query.get_cached_row()).
+    """
+    if not field.rel:
+        return False
+    if field.rel.parent_link:
+        return False
+    if restricted and field.name not in requested:
+        return False
+    if not restricted and field.null:
+        return False
+    return True
+