Feedback-ID: ia2694551:Fastmail
Date: Wed, 26 Jun 2024 15:36:10 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: "David G. Johnston" <david.g.johnston@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, 
	James Coleman <jtc331@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Should we document how column DEFAULT expressions work?
Message-ID: <202406261336.j6nwh25eelo6@alvherre.pgsql>
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On 2024-Jun-25, David G. Johnston wrote:

> On Tue, Jun 25, 2024 at 9:50 PM David Rowley <dgrowleyml@gmail.com> wrote:

> > FWIW, I disagree that we need to write anything about that in this
> > part of the documentation.  I think any argument for doing this could
> > equally be applied to something like re-iterating what the operator
> > precedence rules for arithmetic are, and I don't think that should be
> > mentioned.
> 
> I disagree on this equivalence.  The time literals are clear deviations
> from expected behavior.  Knowing operator precedence rules, they apply
> everywhere equally.  And we should document the deviations directly where
> they happen.  Even if it's just a short link back to the source that
> describes the deviation.  I'm fine with something less verbose pointing
> only to the data types page, but not with nothing.

I agree that it'd be good to have _something_ -- the other stance seems
super unhelpful.  "We're not going to spend two lines to explain some
funny rules that determine surprising behavior here, because we assume
you have read all of our other 3000 pages of almost impenetrably dense
documentation" is not great from a user's point of view.  The behavior
of 'now' in DEFAULT clauses is something that has been asked about for
decades.

Arithmetic precedence is a terrible straw man argument.  Let's put that
aside.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"If it is not right, do not do it.
If it is not true, do not say it." (Marcus Aurelius, Meditations)