Re: Add 64-bit XIDs into PostgreSQL 15

Hi, Robert!
> Lest we miss the forest for the trees, there is an aspect of this
> patch that I find to be an extremely good idea and think we should try
> to get committed even if the rest of the patch set ends up in the
> rubbish bin. Specifically, there are a couple of patches in here that
> have to do with making SLRUs indexed by 64-bit integers rather than by
> 32-bit integers. We've had repeated bugs in the area of handling SLRU
> wraparound in the past, some of which have caused data loss. Just by
> chance, I ran across a situation just yesterday where an SLRU wrapped
> around on disk for reasons that I don't really understand yet and
> chaos ensued. Switching to an indexing system for SLRUs that does not
> ever wrap around would probably enable us to get rid of a whole bunch
> of crufty code, and would also likely improve the general reliability
> of the system in situations where wraparound is threatened. It seems
> like a really, really good idea.

I totally support the idea that the part related to SLRU is worth
committing whether it is being the first step to 64xid or separately.
This subset is discussed in a separate thread [1]. It seems that we
need more time to reach a consensus on the implementation of a whole
big thing. Just this discussion is a complicated thing and reveals
many different aspects concurrently in one thread.

So I'd vote for an evolutionary approach and give my +1 for
undertaking efforts to first committing [1] to 16.

[1]: https://www.postgresql.org/message-id/CAFiTN-uudj2PY8GsUzFtLYFpBoq_rKegW3On_8ZHdxB1mVv3-A%40mail.gmail.com

Kind regards,
Pavel Borisov,
Supabase.