expressions.py 文件源码

def as_sql(self, compiler, connection, template=None, **extra_context):
        connection.ops.check_expression_support(self)
        template_params = self.extra.copy()
        template_params.update(extra_context)
        template_params['subquery'], sql_params = self.queryset.query.get_compiler(connection=connection).as_sql()

        template = template or template_params.get('template', self.template)
        sql = template % template_params
        sql = connection.ops.unification_cast_sql(self.output_field) % sql
        return sql, sql_params