Re: [PERFORM] No hash join across partitioned tables?

(moving to -hackers)

On Wed, Jun 9, 2010 at 4:11 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> In going back through emails I had marked as possibly needing another
>> look before 9.0 is released, I came across this issue again.  As I
>> understand it, analyze (or analyse) now collects statistics for both
>> the parent individually, and for the parent and its children together.
>>  However, as I further understand it, autovacuum won't actually fire
>> off an analyze unless there's enough activity on the parent table
>> considered individually to warrant it.  So if you have an empty parent
>> and a bunch of children with data in it, your stats will still stink,
>> unless you analyze by hand.
>
> Check.
>
>> Assuming my understanding of the problem is correct, we could:
>
>> (a) fix it,
>> (b) document that you should consider periodic manual analyze commands
>> in this situation, or
>> (c) do nothing.
>
>> Thoughts?
>
> The objections to (a) are that it might result in excessive ANALYZE work
> if not done intelligently, and that we haven't got a patch ready anyway.
> I would have liked to get to this for 9.0 but I feel it's a bit late
> now.

I guess I can't really disagree with that. Should we try to document
this in some way?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company