public inbox for [email protected]
help / color / mirror / Atom feedFrom: Tom Lane <[email protected]>
To: David Rowley <[email protected]>
Cc: David G. Johnston <[email protected]>
Cc: James Coleman <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: Should we document how column DEFAULT expressions work?
Date: Wed, 26 Jun 2024 19:38:25 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAApHDvo4z0pU81cfVZTTqWk28oT3rgswtV2nKzSHwDQ=P5aZ=w@mail.gmail.com>
References: <CAAaqYe-wQPbchCUE7pocPNEQ3PMY8a98Txmxc7q0+FvXtk1vvg@mail.gmail.com>
<[email protected]>
<CAAaqYe9_RE2WximHuYRpyfU-H2G+W--49e_8GDqS-vHLOzPvmg@mail.gmail.com>
<[email protected]>
<CAKFQuwZkgm0yqHhf05thqu1gzUK__gXBL5tyBuFvKoOe7Dd6=A@mail.gmail.com>
<CAApHDvoiHYxM2VQYZeiF7JAdP7Y0JxEr86NZpUjoZ9AA4cpzYw@mail.gmail.com>
<[email protected]>
<CAApHDvo4z0pU81cfVZTTqWk28oT3rgswtV2nKzSHwDQ=P5aZ=w@mail.gmail.com>
David Rowley <[email protected]> writes:
> On Wed, 26 Jun 2024 at 17:12, Tom Lane <[email protected]> wrote:
>> Do we want to do anything about
>> nextval()? I guess if you hold your head at the correct
>> angle, that's also a magic-input-value issue, in the sense
>> that the question is when does regclass input get resolved.
> I think I'm not understanding what's special about that. Aren't
> 'now'::timestamp and 'seq_name'::regclass are just casts that are
> evaluated during parse time in transformExpr()?
Right. But there is an example in the manual explaining how
these two things act differently:
'seq_name'::regclass
'seq_name'::text::regclass
The latter produces a constant of type text with a run-time
cast to regclass (and hence a run-time pg_class lookup).
IIRC, we document that mainly because the latter provides a way
to duplicate nextval()'s old behavior of run-time lookup.
Now that I think about it, there's a very parallel difference in
the behavior of
'now'::timestamp
'now'::text::timestamp
but I doubt that that example is shown anywhere.
regards, tom lane
view thread (7+ messages)
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected]
Subject: Re: Should we document how column DEFAULT expressions work?
In-Reply-To: <[email protected]>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox