import: fix upgrade bug for import_file  (#10903)
import: fix upgrade bug for import_file  (#10903)

* fix upgrade bug

Signed-off-by: Little-Wallace <497982b90fc38d39ce68f17ad0ca96c20b76c81b@gmail.com>

* fix lint

Signed-off-by: Little-Wallace <497982b90fc38d39ce68f17ad0ca96c20b76c81b@gmail.com>

* add comment

Signed-off-by: Little-Wallace <497982b90fc38d39ce68f17ad0ca96c20b76c81b@gmail.com>
BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,BusyJay/tikv