Re: Simple postgresql.conf wizard

"Joshua D. Drake" <jd(at)commandprompt(dot)com> writes:

> Actually there are years worth of evidence in these archives. Not that
> the 50 is the right number but that the current settings are definitely
> wrong and that higher ones are needed. That people generally start
> around 100 and go from there, except where they don't and then someone
> like Tom, I or some other person says, "Oh you need to increase
> default_statistics_target".

no, Tom or some other person would say "you need to raise the statistics
target *on that column*" I've never seen any case on the list where raising
the statistics target on every column of every table in every database of the
cluster was warranted.

> There is no empirical evidence that 50 is the right setting but there is
> more than enough anecdotal evidence to suggest that 50 is a lot better
> than 10 and that even higher than 50 is reasonable. In an effort to
> follow the PostgereSQL conservative mantra, 50 is a good compromise.

A factor of 5 increase is conservative? In any case the mantra is "run the
numbers and produce the evidence" not "pick a smaller arbitrary number". I
started to do this for you last week but got side-tracked. Do you have any
time for this?

>> I think the rhetorical answer is "so that we don't fill up the disk",
>
> I don't think at any time I have said to my self, I am going to set this
> parameter low so I don't fill up my disk. If I am saying that to myself
> I have either greatly underestimated the hardware for the task. Consider
> that we are quarreling over what amounts to a nominal amount of hard
> drive space, 1000 checkpoint_segments = 1.6G of space. My phone has more
> capacity than that.

Well my phone has 16G of RAM, why not 10000 ?

Any number you pick will be an arbitrary one. Whatever value you pick it's
going to be "so that we don't fill up the disk" in some form or another.

You know, you actually had me convinced but now you've just convinced me that
we do need this parameter after all.

So how big should a minimum postgres install be not including your data? Is
100M reasonable? Should we say Postgres requires 200M? 500? 1G? Whatever
number we pick (or allow the user to pick) will determine how large this value
ought to be. And incidentally also provide a bound on
autovacuum_max_freeze_age as Heikki pointed out on another thread.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training!