Re: Small improvements to pg_list.h's linitial(), lsecond(), lthird() etc macros

On Tue, 29 Sep 2020 at 12:42, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> David Rowley <dgrowleyml@gmail.com> writes:
> > It does seem fairly low risk and having personally experienced
> > backpatching pain, I understand your motivation to backpatch.  I
> > certainly wouldn't object to backpacking but will defer to your better
> > judgement on whether you choose to or not.
>
> A key point here is that everyplace I'm proposing to touch was already
> changed in v13 (a fortiori, because list_second_cell wasn't there in v12).
> So we can either have two different coding patterns in these areas, or
> three.  Two's better from a backpatching standpoint.  The fact that
> v13 is barely out the door also factors into this ... a year from now,
> my judgment would probably be different.

Yeah, I understand that part.  The pain I was talking about was
writing a patch for master, trying to apply it to the previous version
only to find it does not apply. After fixing it up for that version
trying to apply that patch to the version before that and getting more
conflicts. Repeating that down to our earliest supported version is
something I'd really love to never have to do again. It's an
exhausting process. It's also risky having to custom write a version
of the patch for each release. So I understand and agree with your
reasoning to backpatch as it could reduce the number of versions of a
patch that must be written to fix a bug.  That could reduce the
chances of someone messing up a backpatch at some later date so might
be a safe option. aka. I'm not going to object to you backpatching
this. :)

David