At 06:44 AM 11/24/2009, you wrote:
2009/11/24 Johan De Meersman <vegiv...@tuxera.be>:
> If you are wondering about parallel query execution (that is, splitting a
> single query over multiple cores for faster execution), that is currently
> not supported by MySQL.
[offtopic]
Probably is something stupid, but could that be done with ndb cluster
on a single host? Anyway, I suppose performance loses on distributed
joins and so on would outcome multiple-core benefits. And for most
queries, the bottleneck is usually on disk access, not processor. Has
anybody done any serious testing on this?
Jaime,
Well it all depends on the SQL that is being executed, the table
structure and the size of the query. Now for a particular case you can do
your own benchmarking quite easily to see if disk speed is more relevant
than CPU speed. Copy your tables into a MEMORY table and do the joins
there. Compare that to a disk join (reset the query cache) and see the
improvement. I'm guessing you will probably see a 300% improvement over
disk. As mentioned earlier, MySQL does not scale up very well with multiple
processors which is why it is better to scale out horizontally with clusters.
Mike
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