Re: auto-vacuum & Negative "anl" Values

Hi Tom, Alvaro,

Thanks for your work on this. Please keep me posted as to which
version in CVS this fix will be applied to and I will do my best to
test it.

Thanks again!
--
Dylan Hansen
Enterprise Systems Developer

On 27-Jun-06, at 5:42 AM, Alvaro Herrera wrote:

> Tom Lane wrote:
>> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
>>> + /* last_anl_tuples must never exceed n_live_tuples */
>>
>> If we actually believe the above statement, it seems like your patch
>> to pgstat_recv_tabstat() opens a new issue: with that patch, it is
>> possible for pgstat_recv_tabstat() to decrease n_live_tuples, and
>> therefore a clamp needs to be applied in pgstat_recv_tabstat() too.
>> No?
>
> Hmm, yeah.
>
>> The reason I didn't patch it myself is that I'm not quite clear on
>> what
>> *should* be happening here. What effect should a large delete
>> have on
>> the ANALYZE threshold, exactly? You could argue that a deletion
>> potentially changes the statistics (by omission), and therefore
>> inserts,
>> updates, and deletes should equally count +1 towards the analyze
>> threshold. I don't think we are implementing that though. If we
>> want
>> to do it that way, I suspect last_anl_tuples as currently defined
>> is not
>> the right comparison point.
>
> Maybe what we should do is revert the pgstat_recv_tabstat() part of
> the
> patch in 8.1, and consider redefining last_anl_tuples in HEAD.
> Caffeine
> is not high enough yet to propose anything sensible, but I'll think
> about it a bit later.
>
> --
> Alvaro Herrera http://
> www.CommandPrompt.com/
> PostgreSQL Replication, Consulting, Custom Development, 24x7 support
>
>