Re: slow result

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От Mark Kirkwood
Тема Re: slow result
Дата
Msg-id 45B6ADA7.80204@paradise.net.nz
обсуждение исходный текст
Ответ на slow result  (Laurent Manchon <lmanchon@univ-montp2.fr>)
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Laurent Manchon wrote:
> Hi,
>
> I have a slow response of my PostgreSQL database 7.4 using this query below
> on a table with 800000 rows:
>
> select count(*)from tbl;
>
> PostgreSQL return result in 28 sec every time.


Can you post the results of:

analyze verbose tbl;
explain analyze select count(*) from tbl;

The first will give us some info about how many pages tbl has (in 7.4
ISTR it does not state the # of dead rows... but anyway), the second
should help us deduce why it is so slow.

Also as others have pointed out, later versions are quite a bit faster
for sequential scans...

Cheers

Mark

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