Re: Better default_statistics_target

On Dec 5, 2007 3:26 PM, Greg Sabino Mullane <greg(at)turnstep(dot)com> wrote:
> Agreed, this would be a nice 8.4 thing. But what about 8.3 and 8.2? Is
> there a reason not to make this change? I know I've been lazy and not run
> any absolute figures, but rough tests show that raising it (from 10 to
> 100) results in a very minor increase in analyze time, even for large
> databases. I think the burden of a slightly slower analyze time, which
> can be easily adjusted, both in postgresql.conf and right before running
> an analyze, is very small compared to the pain of some queries - which worked
> before - suddenly running much, much slower for no apparent reason at all.

As Tom stated it earlier, the ANALYZE slow down is far from being the
only consequence. The planner will also have more work to do and
that's the hard point IMHO.

Without studying the impacts of this change on a large set of queries
in different cases, it's quite hard to know for sure that it won't
have a negative impact in a lot of cases.

It's a bit too late in the cycle to change that IMHO, especially
without any numbers.

--
Guillaume