Re: Updating a specific number of rows in pl/pgsql

2009/8/11 D'Arcy J.M. Cain <darcy(at)druid(dot)net>:
> On Mon, 10 Aug 2009 17:52:36 -0700
> "Peter Headland" <pheadland(at)actuate(dot)com> wrote:
>> I can get the rows I want to update like this:
>>
>>   SELECT *
>>    FROM queue
>>    WHERE id = p_queue_id
>>    ORDER BY rank
>>    LIMIT p_number_of_items;
>>
>> Of course, there may not be p_number_of_items available in the queue.
>>
>> I want to update all the rows in the cursor in the same way:
>>
>>   UPDATE queue SET assigned = TRUE;
>
> Assuming that there is a unique identifier on queue, let's call it
> queue_id, you should be able to do something like this:
>
>  UPDATE queue SET assigned = TRUE
>  WHERE queue_id IN (SELECT queue_id
>    FROM queue
>    WHERE id = p_queue_id
>    ORDER BY rank
>    LIMIT p_number_of_items);
>

there are one fast trick
http://www.postgres.cz/index.php/PostgreSQL_SQL_Tricks#Fast_first_n_rows_removing

p.s. replace DELETE by UPDATE
regards
Pavel Stehule

> --
> D'Arcy J.M. Cain <darcy(at)druid(dot)net>         |  Democracy is three wolves
> http://www.druid.net/darcy/                |  and a sheep voting on
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>
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