Re: prevent immature WAL streaming

Hi,

On Thu, Oct 7, 2021 at 6:57 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>
> On 2021-Oct-07, Amul Sul wrote:
>
> > Make sense, thanks for the explanation.
>
> You're welcome.  Also, I forgot: thank you for taking the time to review
> the code.  Much appreciated.

:)

>
>

I have one more question, regarding the need for other global
variables i.e. abortedRecPtr.  (Sorry for coming back after so long.)

Instead of abortedRecPtr point, isn't enough to write
overwrite-contrecord at XLogCtl->lastReplayedEndRecPtr?  I think both
are pointing to the same location then can't we use
lastReplayedEndRecPtr instead of abortedRecPtr to write
overwrite-contrecord and remove need of extra global variable, like
attached?

You might wonder why I am so concerned about the global variable. The
reason is that I am working on another thread[1] where we are trying
to club all the WAL write operations that happen at the end of
StartupXLOG into a separate function. In the future, we might want to
allow executing this function from other processes (e.g.
Checkpointer). For that, we need to remove the dependency of those WAL
write operations having on the global variables which are mostly valid
in the startup process. The easiest way to do that is simply copy all
the global variables into shared memory but that will not be an
optimised solution, the goal is to try to see if we could leverage the existing
information available into shared memory. I would be grateful if you
could share your thoughts on the same, thanks.

Regards,
Amul

1] https://postgr.es/m/CAAJ_b97KZzdJsffwRK7w0XU5HnXkcgKgTR69t8cOZztsyXjkQw@mail.gmail.com