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
a bit of info re mysql and speed with concurrent transactions.
a community site I was working to get running a bit better was using phpnuke and mysql. ( not my site, was a contract )
with 56,000 members the site was bogged down almost to the point of timing out, this was with only 100 or so users online.
another community site, with custom script using mysql backend, sperad over several servers rather than one machine, and 250,000 members. ( 4 terabytes data transfer a month minimum. )
it's often slow responding, but doesn't get close to a timeout.
while these are subjective observations, they show that tuning, and structure of application will have a significant affect, more than would generally be assumed.
mysql is a good application, for lower traffic applications [ local intranet with <100 users ], but I would never actually recommend using mysql on a large database.[ large query useage would be horrendously slow ]
Jaqui
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