+from ldapdb.models.fields import CharField, IntegerField, ListField
+
+def get_lookup_operator(lookup_type):
+ if lookup_type == 'gte':
+ return '>='
+ elif lookup_type == 'lte':
+ return '<='
+ else:
+ return '='
+
+class Constraint(BaseConstraint):
+ """
+ An object that can be passed to WhereNode.add() and knows how to
+ pre-process itself prior to including in the WhereNode.
+ """
+ def process(self, lookup_type, value):
+ """
+ Returns a tuple of data suitable for inclusion in a WhereNode
+ instance.
+ """
+ # Because of circular imports, we need to import this here.
+ from django.db.models.base import ObjectDoesNotExist
+
+ try:
+ if self.field:
+ params = self.field.get_db_prep_lookup(lookup_type, value)
+ db_type = self.field.db_type()
+ else:
+ params = CharField().get_db_prep_lookup(lookup_type, value)
+ db_type = None
+ except ObjectDoesNotExist:
+ raise EmptyShortCircuit
+
+ return (self.alias, self.col, db_type), params
+