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https://issues.apache.org/activemq/browse/CAMEL-2982?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=60837#action_60837
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Christian Mueller commented on CAMEL-2982:
------------------------------------------
Running the
[JpaTest.java|http://svn.apache.org/viewvc/camel/trunk/components/camel-jpa/src/test/java/org/apache/camel/component/jpa/JpaTest.java?view=markup],
we can see the following log comments:
{code}
...
22143 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 232003191>
executing prepstmnt 957929250 SELECT t0.address FROM SendEmail t0 WHERE t0.id =
? [params=(long) 0]
22144 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 232003191> [1
ms] spent
22244 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 824055564>
executing prepstmnt 113256058 SELECT SEQUENCE_VALUE FROM OPENJPA_SEQUENCE_TABLE
WHERE ID = ? FOR UPDATE WITH RR [params=(int) 0]
22246 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 824055564> [1
ms] spent
22326 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 824055564>
executing prepstmnt 1865566999 UPDATE OPENJPA_SEQUENCE_TABLE SET SEQUENCE_VALUE
= ? WHERE ID = ? AND SEQUENCE_VALUE = ? [params=(long) 151, (int) 0, (long) 101]
22338 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 824055564>
[11 ms] spent
22384 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 957509009>
executing prepstmnt 1211729930 INSERT INTO SendEmail (id, address) VALUES (?,
?) [params=(long) 101, (String) [email protected]]
22402 camel TRACE [main] openjpa.jdbc.SQL - <t 533209608, conn 957509009>
[18 ms] spent
...
{code}
using persist instead of merge, you can see the following output (note on the
missing 'SELECT t0.address FROM SendEmail t0 WHERE t0.id = ?'):
{code}
...
13837 camel TRACE [main] openjpa.jdbc.SQL - <t 1954210149, conn 272890728>
executing prepstmnt 1989444474 SELECT SEQUENCE_VALUE FROM
OPENJPA_SEQUENCE_TABLE WHERE ID = ? FOR UPDATE WITH RR [params=(int) 0]
13839 camel TRACE [main] openjpa.jdbc.SQL - <t 1954210149, conn 272890728>
[0 ms] spent
13946 camel TRACE [main] openjpa.jdbc.SQL - <t 1954210149, conn 272890728>
executing prepstmnt 1102050319 UPDATE OPENJPA_SEQUENCE_TABLE SET SEQUENCE_VALUE
= ? WHERE ID = ? AND SEQUENCE_VALUE = ? [params=(long) 251, (int) 0, (long) 201]
13958 camel TRACE [main] openjpa.jdbc.SQL - <t 1954210149, conn 272890728>
[12 ms] spent
14006 camel TRACE [main] openjpa.jdbc.SQL - <t 1954210149, conn 568097598>
executing prepstmnt 436762492 INSERT INTO SendEmail (id, address) VALUES (?, ?)
[params=(long) 201, (String) [email protected]]
14023 camel TRACE [main] openjpa.jdbc.SQL - <t 1954210149, conn 568097598>
[16 ms] spent
...
{code}
Christian
> camel-jpa should support an option to switch from EntityManager.merge(entity)
> to EntityManager.persist(entity)
> --------------------------------------------------------------------------------------------------------------
>
> Key: CAMEL-2982
> URL: https://issues.apache.org/activemq/browse/CAMEL-2982
> Project: Apache Camel
> Issue Type: Improvement
> Components: camel-jpa
> Affects Versions: 2.4.0
> Environment: All
> Reporter: Christian Mueller
> Assignee: Christian Mueller
> Fix For: 2.5.0
>
>
> If you use a 'heavy' normalized database schema, the switch from
> EntityManager.merge(entity) to EntityManager.persist(entity) could bring a
> performance boost.
> The reason is, that by using EntityManager.merge(entity) the EntityManager
> will query the database for each entity if this entity already exists in the
> database. EntityManager.persist(entity) doesn't query the database before the
> entity is persisted.
> In our case, the entities are all new entities, if the Id is null and we
> think we could improve our throughput with this improvement.
> Christian
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