def find_ordering_name(self, name, opts, alias=None, default_order='ASC',
already_seen=None):
"""
Returns the table alias (the name might be ambiguous, the alias will
not be) and column name for ordering by the given 'name' parameter.
The 'name' is of the form 'field1__field2__...__fieldN'.
"""
name, order = get_order_dir(name, default_order)
descending = True if order == 'DESC' else False
pieces = name.split(LOOKUP_SEP)
field, targets, alias, joins, path, opts = self._setup_joins(pieces, opts, alias)
# If we get to this point and the field is a relation to another model,
# append the default ordering for that model unless the attribute name
# of the field is specified.
if field.is_relation and opts.ordering and getattr(field, 'attname', None) != name:
# Firstly, avoid infinite loops.
if not already_seen:
already_seen = set()
join_tuple = tuple(getattr(self.query.alias_map[j], 'join_cols', None) for j in joins)
if join_tuple in already_seen:
raise FieldError('Infinite loop caused by ordering.')
already_seen.add(join_tuple)
results = []
for item in opts.ordering:
results.extend(self.find_ordering_name(item, opts, alias,
order, already_seen))
return results
targets, alias, _ = self.query.trim_joins(targets, joins, path)
return [(OrderBy(t.get_col(alias), descending=descending), False) for t in targets]
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