Re: Disable WAL logging to speed up data loading

At Thu, 19 Nov 2020 11:04:17 -0500, Stephen Frost <sfrost@snowman.net> wrote in 
> Greetings,
> 
> * Laurenz Albe (laurenz.albe@cybertec.at) wrote:
> > On Thu, 2020-11-19 at 05:24 +0000, osumi.takamichi@fujitsu.com wrote:
> > > > > > ereport(WARNING,
> > > > > >          (errmsg("WAL was generated with wal_level=minimal, data may
> > > > > > be missing"),
> > > > > >          errhint("This happens if you temporarily set
> > > > > > wal_level=minimal without taking a new base backup.")));
> > > > > > There's definitely a question about if a WARNING there is really
> > > > > > sufficient or not, considering that you could end up with 'logged'
> > > > > > tables on the replica that are missing data, but I'm not sure that
> > > > > > inventing a new, independent, mechanism for checking WAL level
> > > > > > changes makes
> > > > > sense.
> > > >
> > > > I don't know why WARNING was chosen.  I think it should be FATAL,
> > > > resulting in the standby shutdown, disabling restarting it, and urging the user
> > > > to rebuild the standby.  (I guess that's overreaction because the user may
> > > > not perform operations that lack WAL while wal_level is minimal.)
> > > 
> > > Yeah, I agree that WARNING is not sufficient.
> > 
> > I missed that this is only a warning when I looked at it before.
> > Yes, it should be a fatal error.
> 
> Yeah, the more that I think about it, the more that I tend to agree with
> this.  Does anyone want to argue against changing this into a FATAL..?

I don't come up with a use case where someone needs to set
wal_level=minimal for archive recovery. So +1 to change it to FATAL.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center