Re: [GENERAL] Odd VACUUM behavior when it is expected to truncate last empty pages

Thank you very much, your explanation helped a lot.

This is the tool I needed the solution for
http://code.google.com/p/pc-tools/ if you are interested.

On 4 August 2011 01:10, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> wrote:
> On Wed, Aug 3, 2011 at 12:33 PM, Pavan Deolasee
> <pavan(dot)deolasee(at)gmail(dot)com> wrote:
>>
>>
>> The only problem, other than a surprising behavior that you noted,
>> that I see with this approach is that we might repeatedly try to
>> truncate a relation which in fact does not have anything to truncate.
>> The worst  thing is we might unnecessarily take an exclusive lock on
>> the table.
>>
>
> So it seems we tried to fix this issue sometime back
> http://archives.postgresql.org/pgsql-hackers/2008-12/msg01994.php
>
> But I don't quite understand how the fix would really work.
> nonempty_pages would most likely be set at a value lower than relpages
> if the last page in the relation is all-visible according to the
> visibility map. Did we mean to test (nonempty_pages > 0) there ? But
> even that may not work except for the case when there are no dead
> tuples in the relation.
>
> Thanks,
> Pavan
>
> --
> Pavan Deolasee
> EnterpriseDB     http://www.enterprisedb.com
>

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