Re: Asynchronous and "direct" IO support for PostgreSQL.

Hi Andres,

> > The code is at
> > https://github.com/anarazel/postgres/tree/aio
>
> Just FYI the cfbot says that this version of the patchset doesn't
> apply anymore, and it seems that your branch was only rebased to
> 43c1c4f (Sept. 21th) which doesn't rebase cleanly:

After watching your recent talk "IO in PostgreSQL: Past, Present,
Future" [1] I decided to invest some of my time into this patchset. It
looks like at very least it could use a reviewer, or maybe two :)
Unfortunately, it's a bit difficult to work with the patchset at the
moment. Any chance we may expect a rebased version for the July CF?

> Comments? Questions?

Personally, I'm very enthusiastic about this patchset. However, a set
of 39 patches seems to be unrealistic to test and/or review and/or
keep up to date. The 64 bit XIDs patchset [2] is much less
complicated, but still it got the feedback that it should be splitted
to more patches and CF entries. Any chance we could decompose this
effort?

For instance, I doubt that we need all the backends in the first
implementation. The fallback "worker" one, and io_uring one will
suffice. Other backends can be added as separate features. Considering
that in any case the "worker" backend shouldn't cause any significant
performance degradation, maybe we could start even without io_uring.
BTW, do we need Posix AIO at all, given your feedback on this API?

Also, what if we migrate to AIO/DIO one part of the system at a time?
As I understood from your talk, sequential scans will benefit most
from AIO/DIO. Will it be possible to improve them first, while part of
the system will continue using buffered IO?

[1]: https://www.youtube.com/watch?v=3Oj7fBAqVTw
[2]: https://commitfest.postgresql.org/38/3594/

--
Best regards,
Aleksander Alekseev