Re: count and limit

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От Fabio Victora Hecht
Тема Re: count and limit
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Msg-id d2bb3d100608191756g31f3fbebobd5cf81126f59dd8@mail.gmail.com
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Ответ на Re: count and limit  (Chris <dmagick@gmail.com>)
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Ok, so I think the best that can be done is to EXPLAIN the query and check if it's gonna take long. If it is, I could use the estimated count.

Thanks,

Fabio

On 8/17/06, Chris <dmagick@gmail.com> wrote:
Michael Fuhr wrote:
> On Fri, Aug 18, 2006 at 10:34:44AM +1000, Chris wrote:
>> Fabio Victora Hecht wrote:
>>> I was wondering if there's a way to count the results of a query and
>>> return part of the result set it in one query (LIMIT). Because I usually
>>> have to count the results using one query (to tell the user how many
>>> records match the criteria) and show the first 20 records.
>> I was going to suggest a cursor but I don't think you can get the number
>> of results a cursor has :(
>
> You can but you have to MOVE to the end, so the backend has to visit
> each tuple just as it would for COUNT.  I answered a similar question
> recently:
>
> http://archives.postgresql.org/pgsql-novice/2006-07/msg00220.php
>

Thanks for the pointer :)

I do a lot of those type of things too so this may be a way to handle it
better.

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