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https://issues.apache.org/jira/browse/OPENJPA-1920?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12995878#comment-12995878
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Rick Curtis commented on OPENJPA-1920:
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Ignore my previous comment, I wasn't running the correct scenario.
> N+1 select with entities that contain Maps (even with FetchType.EAGER)
> ----------------------------------------------------------------------
>
> Key: OPENJPA-1920
> URL: https://issues.apache.org/jira/browse/OPENJPA-1920
> Project: OpenJPA
> Issue Type: Improvement
> Components: kernel
> Affects Versions: 2.0.0
> Reporter: Vermeulen
>
> When I have an entity that contains a Map, e.g.:
> @Entity
> public class TestEntity {
> @ElementCollection(fetch = FetchType.EAGER)
> Map<String, String> strings = new HashMap<String, String>();
> }
> And I select all existing entities
> String query = "SELECT z FROM " +
> TestEntity.class.getSimpleName()
> + " z";
> List<TestEntity> result = em.createQuery(query,
> TestEntity.class)
> .getResultList();
> n + 1 selects are performed which can be seen by using <property
> name="openjpa.Log" value="DefaultLevel=TRACE" />
> 917 testPU TRACE [main] openjpa.Query - Executing query: SELECT z FROM
> TestEntity z
> 918 testPU TRACE [main] openjpa.jdbc.SQL - <t 4837279, conn 6040101>
> executing prepstmnt 17507279 SELECT t0.id, t0.name FROM TestEntity t0
> 918 testPU TRACE [main] openjpa.jdbc.SQL - <t 4837279, conn 6040101> [0
> ms] spent
> 919 testPU TRACE [main] openjpa.jdbc.SQLDiag - load field: 'strings' for
> oid=entities.TestEntity-1 class entities.TestEntity
> 919 testPU TRACE [main] openjpa.jdbc.SQL - <t 4837279, conn 6040101>
> executing prepstmnt 7493991 SELECT t0.KEY0, t0.value FROM TestEntity_strings
> t0 WHERE t0.TESTENTITY_ID = ? [params=(long) 1]
> 919 testPU TRACE [main] openjpa.jdbc.SQL - <t 4837279, conn 6040101> [0
> ms] spent
> 920 testPU TRACE [main] openjpa.jdbc.SQLDiag - load field: 'strings' for
> oid=entities.TestEntity-51 class entities.TestEntity
> 920 testPU TRACE [main] openjpa.jdbc.SQL - <t 4837279, conn 6040101>
> executing prepstmnt 7200207 SELECT t0.KEY0, t0.value FROM TestEntity_strings
> t0 WHERE t0.TESTENTITY_ID = ? [params=(long) 51]
> etc.....
> It doesn't matter whether or not I use <property
> name="openjpa.jdbc.EagerFetchMode" value="parallel"/> or <property
> name="openjpa.jdbc.EagerFetchMode" value="join"/>.
> This is extremely inefficient when I wish to load a list of products that
> have their name set in multiple languages by using a Map from language to
> String.
> As a workaround I can turn the Map into a List and search the List myself for
> the right entry.
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