Re: Checksum errors in pg_stat_database

On 4/2/19 7:06 PM, Magnus Hagander wrote:
> On Tue, Apr 2, 2019 at 8:47 AM Michael Paquier <michael(at)paquier(dot)xyz <mailto:michael(at)paquier(dot)xyz>> wrote:
>
> On Tue, Apr 02, 2019 at 07:43:12AM +0200, Julien Rouhaud wrote:
> > On Tue, Apr 2, 2019 at 6:56 AM Michael Paquier <michael(at)paquier(dot)xyz <mailto:michael(at)paquier(dot)xyz>> wrote:
> >>  One thing which is not
> >> proposed on this patch, and I am fine with it as a first draft, is
> >> that we don't have any information about the broken block number and
> >> the file involved.  My gut tells me that we'd want a separate view,
> >> like pg_stat_checksums_details with one tuple per (dboid, rel, fork,
> >> blck) to be complete.  But that's just for future work.
> >
> > That could indeed be nice.
>
> Actually, backpedaling on this one...  pg_stat_checksums_details may
> be a bad idea as we could finish with one row per broken block.  If
> a corruption is spreading quickly, pgstat would not be able to sustain
> that amount of objects.  Having pg_stat_checksums would allow us to
> plugin more data easily based on the last failure state:
> - last relid of failure
> - last fork type of failure
> - last block number of failure.
> Not saying to do that now, but having that in pg_stat_database does
> not seem very natural to me.  And on top of that we would have an
> extra row full of NULLs for shared objects in pg_stat_database if we
> adopt the unique view approach...  I find that rather ugly.
>
>
> I think that tracking each and every block is of course a non-starter, as you've noticed.

I think that's less of a concern now that the stats collector process has gone and that the stats are now collected in shared memory, what do you think?

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
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