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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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