public inbox for [email protected]
help / color / mirror / Atom feedFrom: David Rowley <[email protected]>
To: Peter Eisentraut <[email protected]>
Cc: Tom Lane <[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: Mon, 1 Jul 2024 11:54:50 +1200
Message-ID: <CAApHDvrURTcDn3GTsmXzm9VqT3acLh=T=aUYMuKrtozw0nq8Tg@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
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>
<CAKFQuwbyjn0p5aKz1sKfJHQCTbGy1xhWaNR2xdnXv-X4oPdOGA@mail.gmail.com>
<CAApHDvqShXhOat03iEV1VqXM68DBJ+zM95Ghbu0rcqs8KnhQQQ@mail.gmail.com>
<[email protected]>
<CAApHDvouPRyga3-5ZYLt_RUhU942bk0WPVgro+U=R3cvBRXbeQ@mail.gmail.com>
<[email protected]>
On Thu, 27 Jun 2024 at 23:57, Peter Eisentraut <[email protected]> wrote:
> Maybe we should really be thinking about deprecating these special
> values and steering users more urgently toward more robust alternatives.
>
> Imagine if 'random' were a valid input value for numeric types.
I think there are valid reasons to use the special timestamp input
values. One that I can think of is for use with partition pruning. If
you have a time-range partitioned table and want the planner to prune
the partitions rather than the executor, you could use
'now'::timestamp in your queries to allow the planner to prune. That
works providing that you never use that in combination with PREPARE
and never put the query with the WHERE clause inside a VIEW. I don't
have any other good examples, but I suppose that if someone needed to
capture the time some statement was executed and record that
somewhere, sort of like the __DATE__ and __TIME__ macros in C. Perhaps
that's useful to record the last time some DDL script was executed.
I'd like to know what led someone down the path of doing something
like DEFAULT 'now()'::timestamp in a CREATE TABLE. Could it be a
faulty migration tool that created these and people copy them thinking
it's a legitimate syntax?
David
view thread (17+ messages) latest in thread
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], [email protected]
Subject: Re: Should we document how column DEFAULT expressions work?
In-Reply-To: <CAApHDvrURTcDn3GTsmXzm9VqT3acLh=T=aUYMuKrtozw0nq8Tg@mail.gmail.com>
* 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