1 """

     2 Useful auxilliary data structures for query construction. Not useful outside

     3 the SQL domain.

     4 """

     5 

     6 class EmptyResultSet(Exception):

     7     pass

     8 

     9 class FullResultSet(Exception):

    10     pass

    11 

    12 class MultiJoin(Exception):

    13     """

    14     Used by join construction code to indicate the point at which a

    15     multi-valued join was attempted (if the caller wants to treat that

    16     exceptionally).

    17     """

    18     def __init__(self, level):

    19         self.level = level

    20 

    21 class Empty(object):

    22     pass

    23 

    24 class RawValue(object):

    25     def __init__(self, value):

    26         self.value = value

    27 

    28 class Date(object):

    29     """

    30     Add a date selection column.

    31     """

    32     def __init__(self, col, lookup_type):

    33         self.col = col

    34         self.lookup_type = lookup_type

    35 

    36     def relabel_aliases(self, change_map):

    37         c = self.col

    38         if isinstance(c, (list, tuple)):

    39             self.col = (change_map.get(c[0], c[0]), c[1])

    40 

    41     def as_sql(self, qn, connection):

    42         if isinstance(self.col, (list, tuple)):

    43             col = '%s.%s' % tuple([qn(c) for c in self.col])

    44         else:

    45             col = self.col

    46         return connection.ops.date_trunc_sql(self.lookup_type, col)