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From: Cecil Westerhof <Cecil@decebal.nl>
Newsgroups: comp.lang.java.programmer
Subject: Re: Performance JPA
Date: Fri, 13 Nov 2015 08:30:37 +0100
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On Thursday 12 Nov 2015 07:27 CET, Cecil Westerhof wrote:

> On Thursday 12 Nov 2015 01:10 CET, Arne Vajhøj wrote:
>
>> That persistence.xml does not look correct.
>>
>> <property name="openjpa.ConnectionDriverName"
>> value="com.ibm.db2.jcc.DB2Driver" />
>>
>> specifies a JDBC driver not DataSource.
>>
>> That may (*) make JPA not use WAS connection pool but try to
>> establish a connection for every operation. And that is very bad.
>
> That was what I thought was happening. (A new connection every
> time.)
>
>
>> The technique may work fine for a local database with a simple
>> login protocol but with a remote database and complex protocol,
>> then it could create a huge overhead.
>>
>> But we would need to see the rest of the persistence,xml to be sure
>> (the standard part actually determines whether it is driver or
>> data source).
>>
>> Try see:
>>
>> http://stackoverflow.com/questions/3526434/ibm-websphere-jpa-configuration-how-to-update-persistence-xml
>>
>> for an example of a persistence.xml that looks way
>> more I would expect (no driver, data source, all managed).
>
> I have been trying some things, but until now without success. I
> need to go to the office again and from there I do not have
> newsgroup access, so some silence on my part again. I will
> communicate my progress when I am back home.

Problem solved. I removed openjpa.ConnectionDriverName and
openjpa.jdbc.DBDictionary.

The unit starts with:
    <persistence-unit name="cvu-persistence-test" transaction-type="JTA">
    <description>Persistence Testen</description>
    <jta-data-source>jdbc/cvu/datasource</jta-data-source>

    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <validation-mode>AUTO</validation-mode>
    <properties>

I added transaction-type, jta-data-source and validation-mode.

The validation-mode needs to be entered just before properties,
otherwise it does not work.

The performance is now comparable with the performance of JDBC. So I
proved the naysayers wrong.

OneToMany relations are also going to be implemented, so maybe the JPA
version will be even faster as the JDBC version. ;-)


One question: I removed
    <property name="openjpa.jdbc.DBDictionary" value="org.apache.openjpa.jdbc.sql.DB2Dictionary" />

It works, but I was told that I could better put it back, because it
was used to optimise complex queries. Is this true?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof