Re: [HACKERS] Re: BUG #4796: Recovery followed by backup creates unrecoverable WAL-file

Fujii Masao wrote:
> On Fri, May 15, 2009 at 8:56 PM, Heikki Linnakangas
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>> Fujii Masao wrote:
>>> When only the history file for timeline 6 is deleted, timeline 6 would be
>>> assigned as the newest one *again* at the end of archive recovery.
>>> Is this safe?
>> If you delete history file and all the WAL for timeline 6, yeah, nothing
>> stops it from being reused. It will work just fine, as if it never existed.
>> If you still have the history file and WAL for the old timeline 6 lying
>> around somewhere else like an older offsite backup, it's easy for the
>> administrator to get confused, but there isn't much we can do about that.
>
> OK, I probably understood your point. The timeline history files whose
> timeline ID is larger than that of an oldest backup must not be deleted
> from the archive. On the other hand, the smaller or equal one can be
> deleted. Not all history files are necessary. So, if we don't keep older
> backup, we probably can delete all files in the archive before
> pg_start_backup().
> Is my understanding right?

Yes, that's correct.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com