query.py 文件源码

def resolve_ref(self, name, allow_joins=True, reuse=None, summarize=False):
        if not allow_joins and LOOKUP_SEP in name:
            raise FieldError("Joined field references are not permitted in this query")
        if name in self.annotations:
            if summarize:
                # Summarize currently means we are doing an aggregate() query
                # which is executed as a wrapped subquery if any of the
                # aggregate() elements reference an existing annotation. In
                # that case we need to return a Ref to the subquery's annotation.
                return Ref(name, self.annotation_select[name])
            else:
                return self.annotation_select[name]
        else:
            field_list = name.split(LOOKUP_SEP)
            field, sources, opts, join_list, path = self.setup_joins(
                field_list, self.get_meta(),
                self.get_initial_alias(), reuse)
            targets, _, join_list = self.trim_joins(sources, join_list, path)
            if len(targets) > 1:
                raise FieldError("Referencing multicolumn fields with F() objects "
                                 "isn't supported")
            if reuse is not None:
                reuse.update(join_list)
            col = targets[0].get_col(join_list[-1], sources[0])
            return col