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From Bryan Noll <bwn...@gmail.com>
Subject Re: Data + Query cache
Date Thu, 24 Aug 2006 21:34:03 GMT
I found this 
(http://people.apache.org/~mprudhom/openjpa/site/openjpa-project/manual/ref_guide_caching.html#ref_guide_cache)...

but I was looking for some documentation about what the default cache 
configuration settings would be, and I'm not seeing it there.

The point you made about the behavior being less obvious is not that big 
a deal to me.... I assume that if someone isn't sure what's going on, 
they'll turn on DEGUG or TRACE level logging, and see some kind of 
message like :

"To let you know, this wasn't retrieved from the database, we still had 
the object in the cache, so that's where it is coming from.  By the way, 
if you actually want the performance gains, you better set your logging 
level a little higher."


Two concern I would have would be:

1) How much memory would the default 'cache on' setting consume?  Are 
people going to easily receive OOM errors with the default settings?  (I 
doubt it, but thought it should be mentioned.)
2) What's the default concurrency strategy?  My wife and I making an ATM 
withdrawal or deposit at the same time makes me nervous the farther away 
from transactional we get.

Just some thoughts...

Abe White wrote:
> How does the list feel about turning the L2 data and query caches on 
> by default?  Traditionally, Kodo always left them off by default, 
> primarily because they required a "performance pack" license to run.
>
> One downside of turning the caches on by default is that OpenJPA's 
> behavior becomes less obvious.  Actions like refresh() that users 
> might expect to hit the DB will often be intercepted by the cache 
> instead.  It might confuse some users.  Also, OpenJPA will suck up 
> more memory with the cache on than with it off.  And certain very 
> naïve tests that don't utilize caching can be slightly slower.
>
> Personally, I think providing new users / evaluators with potentially 
> vastly increased performance outweighs the 
> downsides._______________________________________________________________________ 
>
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