Re: BUG #17716: walsender process hang while decoding 'DROP PUBLICATION' XLOG

On Mon, Dec 19, 2022 at 9:58 PM Bowen Shi <zxwsbg12138(at)gmail(dot)com> wrote:
>
> Hello,
> Thanks for your advice. I make some tests and this problem can't be
> reproduced in PG 14+ version. I think adding a new XLOG type will help
> resolve this problem. But I think the following patch may be helpful
> in the PG 13 version.
>
> The invalidation contains two parts: pgoutput and relfilenodeMap. We
> have no way to optimize relfilenodeMap part , since it has been
> discussed in previous mails
> https://www.postgresql.org/message-id/CANDwggKYveEtXjXjqHA6RL3AKSHMsQyfRY6bK+NqhAWJyw8psQ@mail.gmail.com.
>
> However, I'd like to contribute a patch to fix pgoutput part. We can skip
> invalidating caches after first time with a lazy tag and this works.
> It almost doubles the walsender performance while decoding this XLOG.
>

I don't see any obvious problem with your suggested fix but it doesn't
appear to be a very good solution as it will still mark all entries
for an invalidation after any valid DML operation. Also, there doesn't
appear to be much benefit in versions >=v14 (as per tests done till
now). So, instead of partially solving your use case for old versions,
isn't it better if you can upgrade to later versions (>=14)?

--
With Regards,
Amit Kapila.