lookups.py 文件源码

def as_sql(self, compiler, connection):
        sql, params = compiler.compile(self.lhs)
        lhs_output_field = self.lhs.output_field
        if isinstance(lhs_output_field, DateTimeField):
            tzname = timezone.get_current_timezone_name() if settings.USE_TZ else None
            sql, tz_params = connection.ops.datetime_extract_sql(self.lookup_name, sql, tzname)
            params.extend(tz_params)
        elif isinstance(lhs_output_field, DateField):
            sql = connection.ops.date_extract_sql(self.lookup_name, sql)
        elif isinstance(lhs_output_field, TimeField):
            sql = connection.ops.time_extract_sql(self.lookup_name, sql)
        else:
            raise ValueError('DateTransform only valid on Date/Time/DateTimeFields')
        return sql, params