For what should pg_stop_backup wait?

Hi

In HEAD, pg_stop_backup waits until the history file has been archived.
But, in order to ensure that the last wal file was archived, pg_stop_backup
should wait until not only the history file but also the backup stopping wal
file has been archived, I think.

Because the alphabetic order of the history file and the backup stopping
wal file is not constant.

If the backup starting wal file is the same as the stopping one (that is,
any wal files were not switched during backup), the history file whose
name consists of the starting one is behind the stopping one.
Otherwise, the backup stopping wal file is behind the history file.

Is this worth fixing?

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center