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- """
- Useful auxiliary data structures for query construction. Not useful outside
- the SQL domain.
- """
- class Col(object):
- def __init__(self, alias, target, source):
- self.alias, self.target, self.source = alias, target, source
- def as_sql(self, qn, connection):
- return "%s.%s" % (qn(self.alias), qn(self.target.column)), []
- @property
- def output_field(self):
- return self.source
- def relabeled_clone(self, relabels):
- return self.__class__(relabels.get(self.alias, self.alias), self.target, self.source)
- def get_group_by_cols(self):
- return [(self.alias, self.target.column)]
- def get_lookup(self, name):
- return self.output_field.get_lookup(name)
- def get_transform(self, name):
- return self.output_field.get_transform(name)
- def prepare(self):
- return self
- class EmptyResultSet(Exception):
- pass
- class MultiJoin(Exception):
- """
- Used by join construction code to indicate the point at which a
- multi-valued join was attempted (if the caller wants to treat that
- exceptionally).
- """
- def __init__(self, names_pos, path_with_names):
- self.level = names_pos
- # The path travelled, this includes the path to the multijoin.
- self.names_with_path = path_with_names
- class Empty(object):
- pass
- class Date(object):
- """
- Add a date selection column.
- """
- def __init__(self, col, lookup_type):
- self.col = col
- self.lookup_type = lookup_type
- def relabeled_clone(self, change_map):
- return self.__class__((change_map.get(self.col[0], self.col[0]), self.col[1]))
- def as_sql(self, qn, connection):
- if isinstance(self.col, (list, tuple)):
- col = '%s.%s' % tuple(qn(c) for c in self.col)
- else:
- col = self.col
- return connection.ops.date_trunc_sql(self.lookup_type, col), []
- class DateTime(object):
- """
- Add a datetime selection column.
- """
- def __init__(self, col, lookup_type, tzname):
- self.col = col
- self.lookup_type = lookup_type
- self.tzname = tzname
- def relabeled_clone(self, change_map):
- return self.__class__((change_map.get(self.col[0], self.col[0]), self.col[1]))
- def as_sql(self, qn, connection):
- if isinstance(self.col, (list, tuple)):
- col = '%s.%s' % tuple(qn(c) for c in self.col)
- else:
- col = self.col
- return connection.ops.datetime_trunc_sql(self.lookup_type, col, self.tzname)
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