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* NOW vs CURRENT_DATE
@ 2008-08-24 20:01 dforum <dforums@vieonet.com>
0 siblings, 2 replies; 3+ messages in thread
From: dforum @ 2008-08-24 20:01 UTC (permalink / raw)
To: pgsql-performance
Hello every body,
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
0.065 ms
tx
david
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: NOW vs CURRENT_DATE
@ 2008-08-24 21:22 Peter Schuller <peter.schuller@infidyne.com>
parent: dforum <dforums@vieonet.com>
1 sibling, 0 replies; 3+ messages in thread
From: Peter Schuller @ 2008-08-24 21:22 UTC (permalink / raw)
To: dforum <dforums@vieonet.com>; +Cc: 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.schuller@infidyne.com>'
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^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: NOW vs CURRENT_DATE
@ 2008-08-25 06:01 Tino Wildenhain <tino@wildenhain.de>
parent: dforum <dforums@vieonet.com>
1 sibling, 0 replies; 3+ messages in thread
From: Tino Wildenhain @ 2008-08-25 06:01 UTC (permalink / raw)
To: dforum <dforums@vieonet.com>; +Cc: pgsql-performance
Hi,
dforum wrote:
> Hello every body,
>
> 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
Try that with a timestamp - column and use now() and current_timestamp
with a long running query and then compare min(column) max(column) in
both cases :-)
Regards
Tino
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-- links below jump to the message on this page --
2008-08-24 20:01 NOW vs CURRENT_DATE dforum <dforums@vieonet.com>
2008-08-24 21:22 ` Peter Schuller <peter.schuller@infidyne.com>
2008-08-25 06:01 ` Tino Wildenhain <tino@wildenhain.de>
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