Re: 7.3.1 New install, large queries are slow

On Fri, 17 Jan 2003, Tom Lane wrote:

>
> Yeah, but isn't that theory a hangover from pre-Unix operating systems?
> In all modern Unixen, you can expect the kernel to make use of any spare
> RAM for disk buffer cache --- and that behavior makes it pointless for
> Postgres to try to do large amounts of its own buffering.
>

Informix, oracle, etc all do raw device access bypassing the kernels
buffering, etc. So they need heaping gobules of memory to do the same
thing the kernel does.. but since they know the exact patterns of data and
how things will be done they can fine tune their buffer caches to get much
better performance than the kernel (15-20% in informix's case) since the
kernel needs to be a "works good generally"

probably the desire to crank that up stems from using those other db's I
know I used to do that with pgsql. (Ahh, I crank that setting up through
the roof on informix, I'll do the same with pg)

perhaps a FAQ entry or comment in the shipped config about it?
I think if people realize it isn't quite the same as what it does in
oracle/informix/etc then they'll be less inclined to cranking it.

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Jeff Trout <jeff(at)jefftrout(dot)com> http://www.jefftrout.com/
Ronald McDonald, with the help of cheese soup,
controls America from a secret volkswagon hidden in the past
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