Re: Status of issue 4593 - Mailing list pgsql-bugs

From Tom Lane
Subject Re: Status of issue 4593
Date
Msg-id 28503.1231200194@sss.pgh.pa.us
Whole thread Raw
In response to Re: Status of issue 4593  (Jeff Davis <pgsql@j-davis.com>)
Responses Re: Status of issue 4593  (Peter Eisentraut <peter_e@gmx.net>)
List pgsql-bugs
Jeff Davis <pgsql@j-davis.com> writes:
> On Mon, 2009-01-05 at 15:42 -0500, Tom Lane wrote:
>> The only way to avoid this would be to lock before the sort, which could
>> have the effect of locking more rows than are returned (if you also use
>> LIMIT);

> How would that work in the case of an index scan sort?

It wouldn't, which is one of the problems with doing it any other way...

I don't think there's a bug here, at least not in the sense that it
isn't Operating As Designed.  But it does seem like we could do with
some more/better documentation about exactly how FOR UPDATE works.
The sequence of operations is evidently a bit more user-visible than
I'd realized.

            regards, tom lane

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