From: | Peter Schuller <peter(dot)schuller(at)infidyne(dot)com> |
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To: | dforum <dforums(at)vieonet(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: NOW vs CURRENT_DATE |
Date: | 2008-08-24 21:22:43 |
Message-ID: | 20080824212243.GA51548@hyperion.scode.org |
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Thread: | |
Lists: | pgsql-performance |
> I just discover a big not only big huge difference between NOW() and
> CURRENT_DATE.
>
> Did you already know about it and do you know why ?
>
> DELETE FROM blacklist where bl_date < (NOW() - interval '2 DAY');
> on 6 000 000 of records
> 699 ms
>
> 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.
--
/ Peter Schuller
PGP userID: 0xE9758B7D or 'Peter Schuller <peter(dot)schuller(at)infidyne(dot)com>'
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