Re: Mark function arguments of type "Datum *" as "const Datum *" where possible

From: Peter Eisentraut <peter(at)eisentraut(dot)org>
To: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Cc: Nathan Bossart <nathandbossart(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Paquier <michael(at)paquier(dot)xyz>, Postgres hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Mark function arguments of type "Datum *" as "const Datum *" where possible
Date: 2025-10-31 09:56:35
Message-ID: 641abcbf-8044-4c65-895e-683e17b170a1@eisentraut.org
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On 28.09.25 05:02, Chao Li wrote:
>
> On Fri, Sep 26, 2025 at 11:00 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
> <mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>> wrote:
>
> Yeah.  In particular, probably 99% of such Datum arrays also have an
> associated array of bool isnull flags.  IMO it makes exactly zero
> sense to const-ify the Datums without similar protection for their
> isnull flags.
>
>
> Based on Tom's comment, I have made the scope a little broader. If a
> function's "Datum *" parameter is changed to const, then if it has a
> pairing "bool *isnull" parameter, I make it const as well. Also, if the
> function has other pointer parameters that can be const, I change them
> to const as well. See v3 attached.

I have committed this. Note that the documentation for the SPI
functions needed to be updated.

As discussed in the other thread about ItemPointer etc., I removed from
your patch changes that would have broken externally usable callback
function signatures. But that was only a small portion of your patch.

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