Re: Duplicate history file?

Hi Horiguchi-san,

> (To recap: In a replication set using archive, startup tries to
> restore WAL files from archive before checking pg_wal directory for
> the desired file. The behavior itself is intentionally designed and
> reasonable. However, the restore code notifies of a restored file
> regardless of whether it has been already archived or not. If
> archive_command is written so as to return error for overwriting as we
> suggest in the documentation, that behavior causes archive failure.)
>
> After playing with this, I see the problem just by restarting a
> standby even in a simple archive-replication set after making
> not-special prerequisites. So I think this is worth fixing.
>
> With this patch, KeepFileRestoredFromArchive compares the contents of
> just-restored file and the existing file for the same segment only
> when:
>
> - archive_mode = always
> and - the file to restore already exists in pgwal
> and - it has a .done and/or .ready status file.
>
> which doesn't happen usually. Then the function skips archive
> notification if the contents are identical. The included TAP test is
> working both on Linux and Windows.

Thank you for the analysis and the patch.
I'll try the patch tomorrow.

I just noticed that this thread is still tied to another thread
(it's not an independent thread). To fix that, it may be better to
create a new thread again.

Regards,
Tatsuro Yamada