Re: Maintaining cluster order on insert

On Mon, 9 Jul 2007, Tom Lane wrote:

> The hardware is just a Dell x86_64 workstation with crappy IDE disk, so
> maybe things would look better elsewhere, but it's all I have to work
> with.

Do you have write-caching turned off on the drive so INSERTs are being
rate-limited by WAL syncs? Trying to characterize the class of setup
you're using.

The part that seemed curious to me about your results in the unpatched
version is why the first INSERT takes 2.4 seconds, while the second takes
12.2 then later ones settle from 17-23 s. I could understand the 12-23
variation, but that the first one fires off in 2.4 seems kind of fishy;
why so fast? Is there something that's just fitting in memory in that
case that's just missing in the patched version?

results-head:
...
executed DELETE in 14.770937 sec
executed VACUUM in 10.663301 sec
executed INSERT in 2.449248 sec (1st)
...
executed INSERT in 12.212027 sec (2nd)

results-patch:
...
executed DELETE in 18.062664 sec
executed VACUUM in 28.487570 sec
executed INSERT in 25.638022 sec (1st)
...
executed INSERT in 40.759404 sec (2nd)

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD