How should I phrase this?

An alternative, though I'm not sure it's better in any way :

DELETE FROM generators WHERE started + '30 minutes'::interval <= now();

-Mitch

----- Original Message -----
From: "Paul Tomblin" <ptomblin@xcski.com>
To: <pgsql-general@postgresql.org>
Sent: Sunday, July 08, 2001 2:12 PM
Subject: [GENERAL] How should I phrase this?

I've got a table that I insert a value and a timestamp "now()". Then I
want to delete entries that are older than 30 minutes old. After some
experimentation, I found the following works, but it looks awkward and
backwards. Is there a better, more readable way of phrasing this or
rewriting it?

DELETE
FROM generators
WHERE age(now(),started) > interval '30 minutes'

--
Paul Tomblin <ptomblin@xcski.com>, not speaking for anybody
"Nobody can be told what the dominatrix is, they have to see it for

themselves"

Quoting Mitch Vincent (mvincent@cablespeed.com):

An alternative, though I'm not sure it's better in any way :

DELETE FROM generators WHERE started + '30 minutes'::interval <= now();

Well, that looks a little nicer. Thanks.

--
Paul Tomblin <ptomblin@xcski.com>, not speaking for anybody
Q: How did you get into artificial intelligence?
A: Seemed logical -- I didn't have any real intelligence.

Actually, I'd recommend

DELETE FROM generators WHERE started <= now() - '30 minutes'::interval;

This might or might not seem more natural than the other way, but it
has the advantage that there's at least a potential to make use of an
index on the "started" column. In practice, because now() is considered
a non-constant-foldable function by the optimizer, you have to cheat a
little bit to make the righthand side reduce to a constant so that
indexing will actually work. See past discussions in the archives.

regards, tom lane