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From: Robert Haas <robertmhaas@gmail.com>
Date: Mon, 23 Jan 2023 15:41:45 -0500
Message-ID: <CA+TgmoYkocpPWe12MSLPnUDsFTxQMVUf+a3g2bnrPvbG7LcYfw@mail.gmail.com>
Subject: Re: Fix incorrect comment reference
To: James Coleman <jtc331@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
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On Mon, Jan 23, 2023 at 3:19 PM James Coleman <jtc331@gmail.com> wrote:
> On Mon, Jan 23, 2023 at 1:26 PM Robert Haas <robertmhaas@gmail.com> wrote:
> > On Mon, Jan 23, 2023 at 8:31 AM James Coleman <jtc331@gmail.com> wrote:
> > > See the attached for a simple comment fix -- the referenced
> > > generate_useful_gather_paths call isn't in grouping_planner it's in
> > > apply_scanjoin_target_to_paths.
> >
> > The intended reading of the comment is not clear. Is it telling you to
> > look at grouping_planner because that's where we
> > generate_useful_gather_paths, or is it telling you to look there to
> > see how we get the final target list together? If it's the former,
> > then your fix is correct. If the latter, it's fine as it is.
> >
> > The real answer is probably that some years ago both things happened
> > in that function. We've moved on from there, but I'm still not sure
> > what the most useful phrasing of the comment is.
>
> Yeah, almost certainly, and the comments just didn't keep up.
>
> Would you prefer something that notes both that the broader concern is
> happening via the grouping_planner() stage but still points to the
> proper callsite (so that people don't go looking for that confused)?

I don't really have a strong view on what the best thing to do is. I
was just pointing out that the comment might not be quite so obviously
wrong as you were supposing.

-- 
Robert Haas
EDB: http://www.enterprisedb.com