Re: prelimiary performance comparison pgsql vs mysql

On Tue, Mar 15, 2005 at 12:51:03PM -0800, Jeff Davis wrote:
> Be careful assuming that. DB benchmarks are hard to do in a general
> sense. His results probably indicate a general trend, but you should
> test your application yourself to get a real result. His pattern of SQL
> queries might be very different from yours.

Very true.

You may have noticed that I had a very low query rate of 5.8 queries
per second, because some of the queries have 12 tables to join and
take about 20s to run. This tends to work in postgres' favour.
If you have lots have simple queries, it will be better for mysql
and the break even point will be higher.

Also, while on the subject of scaling. I had the opportunity
to try postgres on a 16CPU Altix and couldn't get it to scale
more than about 4x, whereas Oracle got up to about 12x faster

I assume this is because of the NUMA architecture. I was also
told that Oracle had made no special optimizations to accomodate it.

My guess is that because postgres allocates all its shared
buffers as a contiguous chunk, it puts all the load on one
memory bank.
Oracle on the other hand, seems to use lots of smaller regions
which would probably be spread throughout the physical memory.

Perhaps one of the developers could comment on how difficult
it would be to change the shared buffer handling to use multiple
segments. As I'd definitely be willing to give it a go.

-Mark