AW: [OJB-developers] ODMG Performance vs Broker Performance

[Mahler T. <tho...@it...>]

Hi Darius,

> 
> 1) Oracle class cast exception
> I gave Oracle a try with the unit tests. Unfortunately the driver
> throws a ClassCastException while trying to insert an article.price.
> It is declared as a double within the java source, but it is a
> FLOAT within the repository.xml, so the driver gets the wrong sqltype.
> Would anybody bother if I changed it into DOUBLE in the xml?

should be OK if HSQLDB does not complain...
 
> 2) Performance
> That's some kind of cute:
> Some profiling gave me the information that there are almost no
> real hotspots within ojb, 

I have done several walkthroughs where I tried to eliminate HotSpots shown
by JVM in profiling mode.
There are still time-consuming things but they will be VERY hard to change.
So IMHO it will be difficult to get significant improvements to the
PersistenceBroker layer.
But we should of course give it a try...

> Top100 came out of the hsqldb-driver, where
> a lot of string manipulation (equals, buffer expand, ...) is done.
> Unfortunately they hide the performance I am looking for.
> So I thought let's get a 'real professional and fast' driver with 
> a 'real professional and fast' database to put ojb more into the
> spotlight.
>
> See attached how Oracle 8.1.7 is performing on a P4/1.7/640MB
> compared to hsqldb (still the ordinary broker test).
> I would propose we should offer Oracle support only, as ojb does 
> not seem to produce any remarkable overhead here :o)

Works as expected: HSQLDB is inmemory so there are no network latencies etc.
thus the OJB overhead will be higher.
If you have a "real" database like Oracle, the network overhead will
increase and the percential OJB overhead will decrease.

OJB is "better" than native JDBC here because of the caching boost for the
second querying test.

> I doubt, the profiler would tell me anything about ojb ...
> 

I'm sure you will find some hot spots. But I'm also sure most of them can't
be avoided / eliminated.

cheers,

Thomas