Date: Sun, 24 Aug 2008 23:22:43 +0200
From: Peter Schuller <peter.schuller@infidyne.com>
To: dforum <dforums@vieonet.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: NOW vs CURRENT_DATE
Message-ID: <20080824212243.GA51548@hyperion.scode.org>
References: <48B1BE33.3060505@vieonet.com>
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> I just discover a big not only big huge difference between NOW() and=20
> CURRENT_DATE.
>=20
> Did you already know about it and do you know why ?
>=20
> DELETE FROM blacklist where bl_date < (NOW() - interval '2 DAY');
> on 6 000 000 of records
> 699 ms
>=20
> DELETE FROM blacklist where bl_date < (CURRENT_DATE - interval '2 DAY');
> on 6 000 000 of records

Is this a one-off run after each other (e.g. with a ROLLBACK in
between)? If so I suspect the difference is due to caching and if you
re-run the NOW() version it would also be fast.

Also, NOW() is equivalent to CURRENT_TIMESTAMP() rather than
CURRENT_DATE(). Perhaps the date vs. timestamp has some implication of
how they query is planned.

--=20
/ Peter Schuller

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