Re: [GENERAL] autoanalyze criteria

On 02/23/2013 09:30 PM, Jeff Janes wrote:
> Moved discussion from General To Hackers.
>
> On Sat, Feb 23, 2013 at 10:41 AM, Stefan Andreatta
> <s(dot)andreatta(at)synedra(dot)com <mailto:s(dot)andreatta(at)synedra(dot)com>> wrote:
>
>
> On 02/23/2013 05:10 PM, Jeff Janes wrote:
>>
>> Sorry, I got tunnel vision about the how the threshold was
>> computed, and forgot about the thing it was compared to. There
>> is a "secret" data point in the stats collector
>> called changes_since_analyze. This is not exposed in the
>> pg_stat_user_tables. But I think it should be as I often have
>> wanted to see it.
>>
>>
>
> Sounds like a very good idea to me - any way I could help to make
> such a thing happen?
>
>
>
> It should be fairly easy to implement because the other columns are
> already there to show you the way, and if you want to try your hand at
> hacking pgsql it would be a good introduction to doing so.
>
> Look at each instance in the code of n_dead_dup and
> pg_stat_get_dead_tuples, and those are the places where
> changes_since_analyze also need to be addressed, in an analogous
> manner (assuming it is isn't already there.)
>
> git grep 'n_dead_tup'
>
> It looks like we would need to add an SQL function to retrieve the
> data, then incorporate that function into the view definitions that
> make up the pg_stat_user_tables etc. views. and of course update the
> regression test and the documentation.
>
> Other than implementing it, we would need to convince other hackers
> that this is desirable to have. I'm not sure how hard that would be.
> I've looked in the archives to see if this idea was already considered
> but rejected, but I don't see any indication that it was previously
> considered.
>
> (http://www.postgresql.org/message-id/4823.1262132964@sss.pgh.pa.us).
>
> Cheers,
>
> Jeff

Not being a developer, I am afraid, I will not be going to implement it
myself - nor would anybody wish so ;-)

I also searched the archives, but the closest I found is a discussion on
the Admin List starting here:
http://www.postgresql.org/message-id/626919622.7634700.1351695913466.JavaMail.root@alaloop.com

On the other hand, there is quite a lot of discussion about making
autoanalyze more (or less) aggressive - which seems a difficult task to
me, when you cannot even check what's triggering your autoanalyze.

Anybody else interested?

Regards,
Stefan