Date: Tue, 12 Aug 2025 09:49:27 +0000
From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Paquier <michael@paquier.xyz>, Jeff Davis <pgsql@j-davis.com>,
	Greg Sabino Mullane <htamfids@gmail.com>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: Adding locks statistics
Message-ID: <aJsOJ46OmcYrkCME@ip-10-97-1-34.eu-west-3.compute.internal>
References: <aIyNxBWFCybgBZBS@ip-10-97-1-34.eu-west-3.compute.internal>
 <CAKAnmm+USTr5MeKuyrAvbCjHqbSFbZ+czJsV7fPYt9nECQkf-A@mail.gmail.com>
 <87c3170d0645cec732f0d7b2969c75db1b3c86c6.camel@j-davis.com>
 <aJqAei83uRWV93bM@paquier.xyz>
 <3282672.1754956185@sss.pgh.pa.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <3282672.1754956185@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/aJsOJ46OmcYrkCME%40ip-10-97-1-34.eu-west-3.compute.internal>
Precedence: bulk

Hi,

On Mon, Aug 11, 2025 at 07:49:45PM -0400, Tom Lane wrote:
> Michael Paquier <michael@paquier.xyz> writes:
> > On Mon, Aug 11, 2025 at 02:53:58PM -0700, Jeff Davis wrote:
> >> Can you describe your use case? I'd like to understand whether this is
> >> useful for users, hackers, or both.
> 
> > This is a DBA feature, so the questions I'd ask myself are basically:
> > - Is there any decision-making where these numbers would help?  These
> > decisions would shape in tweaking the configuration of the server or
> > the application to as we move from a "bad" number trend to a "good"
> > number trend.
> > - What would be good numbers?  In this case, most likely a threshold
> > reached over a certain period of time.
> > - Would these new stats overlap with similar statistics gathered in
> > the system, creating duplication and bloat in the pgstats for no real
> > gain?
> 
> I'm also wondering why slicing the numbers in this particular way
> (i.e., aggregating by locktype) is a helpful way to look at the data.
> Maybe it's just what you want, but that's not obvious to me.

Thanks for providing your thoughts!

I thought it was more natural to aggregate by locktype because:

- I think that matches how they are categorized in the doc (from a "wait event"
point of view i.e "Wait Events of Type Lock"). 

- It provides a natural drill-down path, spot issues by locktype in the stats and 
then query pg_locks for specific objects when needed.

Does that make sense to you?

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com