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From Armin Waibel <ar...@code-au-lait.de>
Subject Re: OJB usability - part 5 of 5: caching
Date Wed, 15 Oct 2003 17:25:04 GMT
Hi,

On Wed, 15 Oct 2003 09:51:05 -0500, Chris Giordano <giordano@more.net> 
wrote:

...
> With MySQL as a backend datastore, we configured the JDBC driver to log 
> SQL
> and found OJB's use of a cache is extremely limited.  In fact, the only 
> type of
> query that will actually look up an object in the cache is a query by 
> object
> identity 
> (Reference:org.apache.ojb.broker.core.PersistenceBrokerImpl.getObjectByIdentity()).
>
This is intended. How should OJB perform an sql-query against the
ObjectCache? What we are doing is perform the query, read pk-values
 from the ResultSet, build Identity object, lookup cache, if not found
materialize the whole object.

See RSIterator#getObjectFromResultSet()


> We found that using OJB within Tomcat was such a performance drain it 
> clearly
> wasn't scalable by any measure.  This was the single most determining 
> reason why
> we've backed out of using OJB entirely.
Think that's clearly wrong.
- You can configure the PersistenceBroker-pool,
the connection-pool (depends on the used ConnectionFactory).
- PersistenceBroker
instances are decoupled from connections.
- Most of the
main classes are pluggable (if you want to do some strange things ;-)).
- OJB was used in clusters, distributed cache implementation and howto
posted by Jason McKerr
- support for stored procedures was added (ok, this
breaking the rc rules)
...



> The use of the cache is going to be
> critical if OJB is going to prove itself scalable for high volume 
> production
> use.  In fact, we're simply at a loss as to why anyone would logically 
> choose
> OJB for their next development effort due to this alone.
>
> The OJB documentation is extremely deficient in describing the use of the
> cache.  It implies a much broader implementation and is very 
> misleading.  The
> recommendation here is for clear and thorough documentation - complete 
> with
> limitations of usage, performance benchmarks, expectations etc.
>
I don't agree, the basic behaviour of some cache implementations
are explained, but you are right saying this is not enough. That's the
reason for the "important note: this document is not finished yet"
note at the beginning of the ObjectCache document.

regards,
Armin


> Chris Giordano
> giordano@more.net
>
>
>
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