Re: Remove secondary checkpoint

From: pgsql-hackers-owner(at)postgresql(dot)org
> [mailto:pgsql-hackers-owner(at)postgresql(dot)org] On Behalf Of Michael Paquier
> On Tue, Oct 24, 2017 at 5:58 PM, Tsunakawa, Takayuki
> <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
> > If the latest checkpoint record is unreadable (the WAL
> segment/block/record is corrupt?), recovery from the previous checkpoint
> would also stop at the latest checkpoint. And we don't need to replay the
> WAL records between the previous checkpoint and the latest one, because
> their changes are already persisted when the latest checkpoint was taken.
> So, the user should just do pg_resetxlog and start the database server when
> the recovery cannot find the latest checkpoint record and PANICs?
>
> Not necessarily. If a failure is detected when reading the last checkpoint,
> as you say recovery would begin at the checkpoint prior that and would stop
> when reading the record of last checkpoint, still one could use a
> recovery.conf with restore_command to fetch segments from a different
> source, like a static archive, as only the local segment may be corrupted.

Oh, you are right. "If the crash recovery fails, perform recovery from backup."

Anyway, I agree that the secondary checkpoint isn't necessary.

Regards
Takayuki Tsunakawa