Date: Tue, 15 Jul 2025 12:12:06 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Sami Imseih <samimseih@gmail.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Improve LWLock tranche name visibility across backends
Message-ID: <aHaL5uFCaj_cfueU@nathan>
References: <aHDYHKdEyZiV/Aob@ip-10-97-1-34.eu-west-3.compute.internal>
 <CAA5RZ0vK_EuHwGj8nWkb1UwYjDbqvj+ZyiYPYn3CRsU8uwKUsQ@mail.gmail.com>
 <aHGJBt37dg37f1bE@nathan>
 <CAA5RZ0uic7Us255mFPJSrMFH7UY-RR8YZcjBzNDzfE4gFREDGQ@mail.gmail.com>
 <aHVeqtsltQyBBvAM@nathan>
 <CAA5RZ0vb_CVR7SuCpHrLbV4yDQJ8o9WUudz51YRjUr4PLiDMYg@mail.gmail.com>
 <aHV5BsKoSeOkIsNL@nathan>
 <CAA5RZ0sjBirbsZa0su1yV2UEQFcVmy-HkeQNS+SD5oAxQaRYPQ@mail.gmail.com>
 <aHaIe44bAENt8JPW@nathan>
 <CAA5RZ0v2JdAFh9yBsgvqNXrF68SKoF+bbjhn7ZBW_Oo66XUhrQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: 
 <CAA5RZ0v2JdAFh9yBsgvqNXrF68SKoF+bbjhn7ZBW_Oo66XUhrQ@mail.gmail.com>
Archived-At: <https://www.postgresql.org/message-id/aHaL5uFCaj_cfueU%40nathan>
Precedence: bulk

On Tue, Jul 15, 2025 at 12:06:00PM -0500, Sami Imseih wrote:
> On Tue, Jul 15, 2025 at 11:57 AM Nathan Bossart
> <nathandbossart@gmail.com> wrote:
>> I was imagining putting the array in one big DSA allocation instead of
>> carting around a pointer for each tranche name.  (Sorry, I realize I am
>> hand-waving over some of the details.)
> 
> I understood it like this. Here is a sketch:
> 
> ```
> dsa_pointer p;
> 
> dsa = dsa_create(....)
> 
> p = dsa_allocate(dsa, LWLockTranchesInitialSize());
> tranche_names = (char **) dsa_get_address(dsa, p);
> tranche_names[0] = "my tranche";
> tranche_names[1] = "my tranche";
> ```
> 
> We will need to track the size and resize if needed.
> 
> Is this what you mean, from a high level?

Yes, that's roughly what I had in mind.  We might need to employ some
tricks to avoid a limit on tranche name length, but maybe that's not worth
the energy.

-- 
nathan