| From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
|---|---|
| To: | Michael Glaesemann <grzm(at)seespotcode(dot)net> |
| Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Patches <pgsql-patches(at)postgresql(dot)org>, Jeff Davis <pgsql(at)j-davis(dot)com> |
| Subject: | Re: Synchronized scans |
| Date: | 2007-06-04 21:34:55 |
| Message-ID: | 4664857F.4020208@enterprisedb.com |
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| Thread: | |
| Lists: | pgsql-patches |
Michael Glaesemann wrote:
>> I think the warning on LIMIT without ORDER BY is a good idea,
>> regardless of the synchronized scans patch.
>
> I'm not saying this isn't a good idea, but are there other places where
> there might be gotchas for the unwary, such as DISTINCT without ORDER BY
> or (for an unrelated example) UNION versus UNION ALL? How many of these
> types of messages would be useful?
LIMIT without ORDER BY is worse because it not only returns tuples in
different order, but it can return different tuples altogether when you
run it multiple times.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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