Re: Add sub-transaction overflow status in pg_stat_activity

Nathan Bossart <bossartn@amazon.com>

From: "Bossart, Nathan" <bossartn@amazon.com>
To: Dilip Kumar <dilipbalaut@gmail.com>, Nikolay Samokhvalov <samokhvalov@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-12-07T17:24:36Z
Lists: pgsql-hackers
On 12/6/21, 8:19 PM, "Dilip Kumar" <dilipbalaut@gmail.com> wrote:
> If the subtransaction cache is overflowed in some of the transactions
> then it will affect all the concurrent queries as they need to access
> the SLRU for checking the visibility of each tuple.  But currently
> there is no way to identify whether in any backend subtransaction is
> overflowed or what is the current active subtransaction count.
> Attached patch adds subtransaction count and subtransaction overflow
> status in pg_stat_activity.  I have implemented this because of the
> recent complain about the same[1]

I'd like to give a general +1 to this effort.  Thanks for doing this!
I've actually created a function to provide this information in the
past, so I will help review.

Nathan

Commits

  1. Fix comment that was missing a word.

  2. Expose some information about backend subxact status.