Re: Something is wrong with wal_compression

On Thu, Jan 26, 2023 at 04:14:57PM -0800, Andrey Borodin wrote:
> If we agree that xid allocation is not something persistent, let's fix
> the test? We can replace a check with select * from pg_class or,
> maybe, add an amcheck run.
> As far as I recollect, this test was introduced to test this new
> function in 857ee8e391f.

My opinion would be to make this function more reliable, FWIW, even if
that involves a performance impact when called in a close loop by
forcing more WAL flushes to ensure its report durability and
consistency. As things stand, this is basically unreliable, and we
document it as something applications can *use*. Adding a note in the
docs to say that this function can be unstable for some edge cases
does not make much sense to me, either. Commit 857ee8e itself says
that we can use it if a database connection is lost, which could
happen on a crash..
--
Michael