Re: Add sub-transaction overflow status in pg_stat_activity

On Mon, Nov 14, 2022 at 9:41 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Mon, Nov 14, 2022 at 11:35 AM Amit Singh <amitksingh(dot)mumbai(at)gmail(dot)com>
> wrote:
> > Making the information available in pg_stat_activity makes it a lot
> easier to identify the pid which has caused the subtran overflow. Debugging
> through the app code can be an endless exercise and logging every statement
> in postgresql logs is not practical either. If the overhead of fetching the
> information isn't too big, I think we should consider the
> subtransaction_count and is_overflowed field as potential candidates for
> the enhancement of pg_stat_activity.
>
> The overhead of fetching the information is not large, but Justin is
> concerned about the effect on the display width. I feel that's kind of
> a lost cause because it's so wide already anyway, but I don't see a
> reason why we need *two* new columns. Can't we get by with just one?
> It could be overflowed true/false, or it could be the number of
> subtransaction XIDs but with NULL instead if overflowed.
>
> Do you have a view on this point?
>
>
NULL when overflowed seems like the opposite of the desired effect, calling
attention to the exceptional status. Make it a text column and write
"overflow" or "###" as appropriate. Anyone using the column is going to
end up wanting to special-case overflow anyway and number-to-text
conversion aside from overflow is simple enough if a number, and not just a
display label, is needed.

David J.