MIME-Version: 1.0
References: <662101e2-5ca5-4bf5-9307-2519efde8690@ya.ru> <8687df7d49bc4b28b41c7cf4e9ad1e15d383b2fa.camel@cybertec.at>
 <Z/bk5E6pqIBWTF3j@ubby> <c857b827-3a17-4600-aa98-d0710216ccfe@aklaver.com>
 <Z/foWNmbdDOWH6/M@ubby> <CAKFQuwa-H6ZzST_dFNhviqQ8b4fPfLT+o3btfygrVOxQJhgWNQ@mail.gmail.com>
 <CAHyXU0ypfKJ6LmEWJHKF63m5UEcZwB5gny3DWGQygvVeePM8mw@mail.gmail.com> <752812.1744343513@sss.pgh.pa.us>
In-Reply-To: <752812.1744343513@sss.pgh.pa.us>
From: Dominique Devienne <ddevienne@gmail.com>
Date: Fri, 11 Apr 2025 09:59:18 +0200
Message-ID: <CAFCRh-_H5m_+z=JkKSpmrK=D6nLje1kG11tiCwkC2OXBSD5Ttw@mail.gmail.com>
Subject: Re: Interesting case of IMMUTABLE significantly hurting performance
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Merlin Moncure <mmoncure@gmail.com>, "David G. Johnston" <david.g.johnston@gmail.com>, 
	Nico Williams <nico@cryptonector.com>, Adrian Klaver <adrian.klaver@aklaver.com>, 
	Laurenz Albe <laurenz.albe@cybertec.at>, Olleg Samoylov <splarv@ya.ru>, 
	"pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Archived-At: <https://www.postgresql.org/message-id/CAFCRh-_H5m_%2Bz%3DJkKSpmrK%3DD6nLje1kG11tiCwkC2OXBSD5Ttw%40mail.gmail.com>
Precedence: bulk

On Fri, Apr 11, 2025 at 5:52=E2=80=AFAM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Merlin Moncure <mmoncure@gmail.com> writes:
> > I guess the real problems here are lack of feedback on a number of fron=
ts:
> > *) the server knows the function is not immutable but lets you create i=
t
> > anyway, even though it can have negative downstream consequences
>
> That's debatable I think.  If you know what you're doing, you're going
> to be annoyed by warnings telling you that you don't.

True, but that's typically what pragmas in the code are for then,
to explicitly suppress warnings.

Or a new option in the CREATE FUNCTION command. Better safe than sorry,
and I prefer useful "on-by-default" warnings for the non-experts,
which can be disabled, than silence.

PS: And FWIW, I removed all attributes from the functions I'm
writting, based on your aerlier advice Tom.