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From Francesco Chicchiriccò <ilgro...@apache.org>
Subject Re: H2 poor performance?
Date Thu, 26 Jan 2012 10:49:24 GMT
On 25/01/2012 18:48, Kevin Sutter wrote:
> That is interesting data, Francesco.  Since the actual query processing
> seems to take less time with H2 (vs MySQL), but the overall time of the
> test takes more time with H2 (vs MySQL), my next guess is with Connection
> management.  Maybe the cost of creating Connections is much more expensive
> with H2.  I would also lump in the creation of the EntityManagers, but that
> should be constant between H2 and MySQL.  Except for the creation and
> management of the database Connection.
>
> So, you could try a couple of things.  One thing would be to utilize DBCP
> for pooling your Connections [1].  OpenJPA does not provide connection
> pooling.  We rely on DBCP or an Application Server to provide that level of
> function.  After the initial creation of the Connections, then the pooling
> and sharing of connections would be a constant between H2 and MySQL.
>
> Depending on your test application, the other thing you might try is the
> use of the ConnectionRetainMode set to "always" [2].  If you are constantly
> deleting and re-creating EMs, then this property may not be of use.  But,
> if you are using a single EM for your tests, then keeping a single
> Connection around should help with your overall through-put.

Hi Kevin,
unfortunately applying either (or both) indications does not affect
significantly the overall test execution time (from 117 secs to 110, at
most).

At this point I don't know how to proceed further with investigations:
after all it's all test performance :-(

Thanks anyway: I'll let you know if I eventually find something.

Regards.

> [1]
> http://openjpa.apache.org/builds/latest/docs/manual/manual.html#ref_guide_integration_dbcp
> [2]
> http://openjpa.apache.org/builds/latest/docs/manual/manual.html#ref_guide_dbsetup_retain
>
> 2012/1/25 Francesco Chicchiriccò <ilgrosso@apache.org>
>
>> On 24/01/2012 15:54, Kevin Sutter wrote:
>>
>>> First of all, Congratulations on your migration from Hibernate to OpenJPA.
>>>  I'm glad to hear that things worked out well for you during this effort.
>>>
>> Hi Kevin,
>> thanks for your answer.
>>
>>
>>  As far as H2 performance...  My guess is that the H2 Dictionary may not
>>> have been kept up to date with improvements to H2 features and SQL
>>> improvements.  These dictionaries have been maintained as needs arise and
>>> as expertise provides input and feedback.  For example, our DB2 customers
>>> provide input for the DB2 dictionary, Oracle users provide input for the
>>> Oracle dictionary, etc.  I looked back on my notes and I don't see an
>>> expert identified for H2.  Would you like to provide that service?  :-)
>>>
>> Well, I am not an H2 expert at all: I am just using it for integration
>> tests...
>> Anyway, if I ever find something interesting on this topic, be sure that
>> I'll do my best for providing an adequate patch ;-)
>>
>>
>>
>>  Since the performance of MySQL and Postgres seem to be acceptable, I would
>>> assume that the deficiencies are probably localized to the dictionary.  I
>>> would start by turning on Trace while running your test bucket.  The full
>>> Trace output will show the timings for executing the various SQL.  Maybe
>>> you'll find SQL being generated that is not efficient for H2.  You could
>>> also review the H2 Dictionary and see if some of the basic properties may
>>> not be set correctly for H2.  Maybe comparing MySQL and/or Postgres
>>> dictionaries and trace output with H2's.
>>>
>> Following your advices, I've put log4jdbc [2] at work and found that,
>> quite interestingly, the total time spent in querying H2 is quite less than
>> the total time spent in querying MySQL.
>> Since, as said before, the total time taken by tests is less with MySQL
>> than with H2, I think that there must be some kind of latency.
>>
>> Does this say something more?
>>
>> Thanks.
>> Regards.
>>
>>
>>  2012/1/24 Francesco Chicchiriccò<ilgrosso@apache.**org<ilgrosso@apache.org>
>>>  Hi all,
>>>> I am currently facing some strange behavior with in-memory H2.
>>>>
>>>> In my project - Syncope Open Source IdM [1] - we recently moved from
>>>> Hibernate to OpenJPA: everything is now working and I can safely say
>>>> that the porting is functionally complete.
>>>>
>>>> Our source code does some integration tests with Tomcat 7 and an
>>>> in-memory H2 instance: unfortunately H2 performs really bad in such
>>>> circumstances. Only consider that all tests take 128 secs to run, while
>>>> same tests take only 96 secs with PostgreSQL and 77 with MySQL.
>>>>
>>>> When running the same test suite against last Hibernate-based build, it
>>>> turns out instead that H2 is faster than MySQL and PostgreSQL (as I
>>>> would expect given the small test dataset).
>>>>
>>>> Is there anything special I should take care of when using in-memory H2?
>>>>
>>>> TIA.
>>>> Regards.
>>>>
>>>> [1] http://www.syncope-idm.org
>>>>
>>> [2] http://code.google.com/p/**log4jdbc/<http://code.google.com/p/log4jdbc/>
-- 
Francesco Chicchiriccò

Apache Cocoon Committer and PMC Member
http://people.apache.org/~ilgrosso/


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