From: | Adam Rich <adam(dot)r(at)sbcglobal(dot)net> |
---|---|
To: | Emanuel Calvo Franco <postgres(dot)arg(at)gmail(dot)com> |
Cc: | postgresql Forums <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: limit-offset different result sets with same query |
Date: | 2009-05-08 21:36:10 |
Message-ID: | 4A04A5CA.7030705@sbcglobal.net |
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Lists: | pgsql-general |
Emanuel Calvo Franco wrote:
>
> Executing 'select * from datos limit 1 offset 150000' two times i
have different
> result sets.
> When i execute 'explain analyze verbose <query>' i see that (as
> expected) the seq scan
> is occurring.
>
>
> That's correct? Is logical that if the scan is sequential in the
> physical table returns differents
> data?
>
> I test it on 8.4 beta1 and 8.3.5 and 8.3.7 with the same results.
>
> Thanks in advance.
>
Emanuel,
LIMIT and OFFSET are stable only when you have "ORDER BY" on unique
values. Without that, the database is free to return the rows in
whatever order it deems best, which gives unpredictable results when
combined with LIMIT/OFFSET.
Adam
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