Message-ID: <d78edccb-27c0-4c9c-baee-1ce7745c8cc4@iki.fi>
Date: Thu, 26 Mar 2026 18:57:51 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: Clean up NamedLWLockTranche stuff
To: Sami Imseih <samimseih@gmail.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>,
 Robert Haas <robertmhaas@gmail.com>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
References: <47aaf57e-1b7b-4e12-bda2-0316081ff50e@iki.fi>
 <acVEqGemyK-Yjswa@nathan> <adab98a3-a0e3-4455-9b63-ae6f1ecd18c9@iki.fi>
 <CAA5RZ0ueB84OUews-mS0+ojeWaDtcoV1qY4CNZD8PrdGcaXW-g@mail.gmail.com>
Content-Language: en-US
From: Heikki Linnakangas <hlinnaka@iki.fi>
In-Reply-To: 
 <CAA5RZ0ueB84OUews-mS0+ojeWaDtcoV1qY4CNZD8PrdGcaXW-g@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Archived-At: 
 <https://www.postgresql.org/message-id/d78edccb-27c0-4c9c-baee-1ce7745c8cc4%40iki.fi>
Precedence: bulk

Thanks!

On 26/03/2026 18:34, Sami Imseih wrote:
>> I propose the attached refactorings to make this less confusing. See
>> commit messages for details.
> 
> I only took a look at 0001 so far, and I do agree with this statement
> in the commit message:
> 
> "The "user defined" term was already used in LWTRANCHE_FIRST_USER_DEFINED,
> so let's standardize on that to mean tranches allocated with either
> RequestNamedLWLockTranche() or LWLockNewTrancheId()."
> 
> I do wonder if 0001 is going far enough though.
> 
> Instead of just standardizing that "user defined" could mean tranches allocated
> with RequestNamedLWLockTranche() or LWLockNewTrancheId(), how about we also
> rename these APIs to reflect that as well? This way we remove all concept of
> "named tranche" which is what it sounds like to me you are proposing.
> 
> rename RequestNamedLWLockTranche() to RequestUserDefinedLWLockTranche()
> and LWLockNewTrancheId() to RegisterUserDefinedLWLockTranche()

I'd rather not change RequestNamedLWLockTranche(), because I think 
LWLockNewTrancheId() is better and should be used in new code. I 
consider RequestNamedLWLockTranche() to be a legacy function, for 
backwards compatibility.

> RequestNamedLWLockTranche() requests the lwlock at shmem_request time,
> which is later registered via LWLockNewTrancheId() when lwlocks are
> initialized by the postmaster.
> 
> Also, the name LWLockNewTrancheId() is selling what this function does
> too short.
> It does return a new tranche ID, but it also takes in a user-defined tranche
> name and copies ("registers") that name into LWLockTrancheNames.
> 
> v19 is already changing the signature of LWLockNewTrancheId(), so maybe
> improving the names of these APIs makes sense to do.

Oh, I didn't realize we changed the LWLockNewTrancheId() signature! 
Yeah, if we're changing it anyway, we might as well rename it. I'm not 
sure if I like RegisterUserDefinedLWLockTranche() better, but let's 
think it through.

- Heikki