Re: Different results from identical matviews

On Thursday, July 2, 2020, Anders Steinlein <anders(at)e5r(dot)no> wrote:

>
>
>> Thanks for the tip, but I'm having a hard time thinking that's the case,
>> seeing as I'm unable to trigger the wrong result no matter how hard I try
>> with a new definition/manual query. I've introduced random ordering to the
>> first CTE-clause (where the initial citext values comes from, and casing
>> thus could differ in some order) which doesn't change the result.
>>
>
> I just wanted to add that we're on Postgres 12.3. This matview has been
> with us since 9.4 days, and we have not experienced any such issues before
> (could be customers who haven't noticed or reported it to us, of course...).
> version
>
> ------------------------------------------------------------
> ---------------------------------------------------------------------
> PostgreSQL 12.3 (Ubuntu 12.3-1.pgdg18.04+1) on x86_64-pc-linux-gnu,
> compiled by gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0, 64-bit
>

I concur that the determinism doesn’t seem like a problem - but not much
else does either. As a shot in the dark does pg_depend show any
differences between the dependencies for the two views?

How did this migrate from 9.4 to 12?

It would be helpful if “Explain analyze refresh materialized view” were a
thing (is it?)

If you can backup and restore the existing database (basebackup is more
likely, but pg_dump would be more useful) and still observe the problem
then maybe I see hope for digging down into the cause. Otherwise I’d limit
my decision to testing for the symptom with the solution being to rebuild
any problem views.

David J.