Re: querying the age of a row

From: Alban Hertroys <alban(at)magproductions(dot)nl>
To: "John D(dot) Burger" <john(at)mitre(dot)org>
Cc: PostgreSQL General <pgsql-general(at)postgresql(dot)org>
Subject: Re: querying the age of a row
Date: 2007-06-08 08:11:26
Message-ID: 46690F2E.9010004@magproductions.nl
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John D. Burger wrote:
> In any event, you say you need to know when a row is less than 24 hours
> old - that is presumably not an issue for these old rows. I would add
> the column as suggested, but set it to some time in the past for the
> existing rows. Or, you can set it to NULL, appropriately if you
> interpret NULL as unknown, and test the age with something like this:
>
> where (age(coalesce(ts, '-infinity'::timestamp)) < '24 hours'::interval

...and actually you wouldn't even need the coalesce, as

NULL < '24 hours'::interval IS NULL

...which is considered FALSE by the WHERE clause. It's probably wiser
not to rely on that in your code though, it can be confusing ;)

--
Alban Hertroys
alban(at)magproductions(dot)nl

magproductions b.v.

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