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https://issues.apache.org/jira/browse/OPENJPA-2179?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13264718#comment-13264718
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Mark Struberg commented on OPENJPA-2179:
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I've now committed a unit test which shows the problem. The new
TestOracleDistinctJoin also contains a guide howto invoke this test on the
commandline.
The test will give the following output (amonst others), where you can clearly
see that SomeEmbeddable get's fetched via a separate SQL statement, even though
there is no LAZY loading set on the Embedded field:
1348 test TRACE [main] openjpa.Query - Executing query: select c from
Lecturer l join l.course c
1348 test TRACE [main] openjpa.jdbc.SQL - <t 270142182, conn 754307120>
executing prepstmnt 960389670 SELECT t1.ID, t1.OPTLOCK, t1.COURSENUMBER,
t1.NORMALATTRIBUTE FROM SMSGW.Lecturer t0, SMSGW.Course t1 WHERE t0.COURSE_ID =
t1.ID
1350 test TRACE [main] openjpa.jdbc.SQL - <t 270142182, conn 754307120> [2
ms] spent
1350 test TRACE [main] openjpa.jdbc.SQLDiag - load: class
org.apache.openjpa.jdbc.oracle.SomeEmbeddable oid: 2551
1350 test TRACE [main] openjpa.jdbc.SQL - <t 270142182, conn 754307120>
executing prepstmnt 2034408626 SELECT t0.OBJECTIVEDE, t0.OBJECTIVEEN FROM
SMSGW.Course t0 WHERE t0.ID = ? [params=?]
1351 test TRACE [main] openjpa.jdbc.SQL - <t 270142182, conn 754307120> [1
ms] spent
1354 test TRACE [main] openjpa.jdbc.SQLDiag - load: class
org.apache.openjpa.jdbc.oracle.Course oid: 2551
1354 test TRACE [main] openjpa.jdbc.SQLDiag - Eager relations:
[org.apache.openjpa.jdbc.oracle.Course.lecturers]
1354 test TRACE [main] openjpa.jdbc.SQL - <t 270142182, conn 754307120>
executing prepstmnt 698114403 SELECT t0.LOBCOLUMN, t1.COURSE_ID, t1.POSITION,
t1.ID, t1.OPTLOCK, t1.NAME FROM SMSGW.Course t0, SMSGW.Lecturer t1 WHERE t0.ID
= ? AND t0.ID = t1.COURSE_ID(+) ORDER BY t1.COURSE_ID ASC, t1.POSITION ASC
[params=?]
1355 test TRACE [main] openjpa.jdbc.SQL - <t 270142182, conn 754307120> [1
ms] spent
> 'distinct' and 'join' combinations lead lots of unneccessary sub-queries for
> @Embedded and @Lob fields
> ------------------------------------------------------------------------------------------------------
>
> Key: OPENJPA-2179
> URL: https://issues.apache.org/jira/browse/OPENJPA-2179
> Project: OpenJPA
> Issue Type: Bug
> Components: kernel
> Affects Versions: 2.2.0
> Reporter: Mark Struberg
> Assignee: Mark Struberg
> Fix For: 2.3.0
>
> Attachments: OPENJPA-2179-test-1.patch
>
>
> I have an Entity (Course) with a simple @Embedded field and a @Lob. I do not
> use any LAZY attribution on them!
> If I do a normal em.find, the entity will be loaded as a whole (all the
> fields, including the embedded and the lob will be fetched immediately).
> Sidenote: the Lecturer referred in the select is defined as
> @OneToMany(mappedBy = "course",
> cascade = {CascadeType.PERSIST, CascadeType.REMOVE,
> CascadeType.MERGE},
> orphanRemoval = true, fetch = FetchType.EAGER)
> @OrderColumn(name = "POSITION")
> private List<Lecturer> lecturers;
> The following selects DO work
> * "select c from Course c join c.lecturers l "
> * "select distinct c from Course c"
> The following selects create tons of subqueries! 1 separate sub-query for
> each @Embedded field, and also for each @Lob
> * "select distinct c from Course c join c.lecturers l "
> * "select distinct c from Lecturer l join l.course c"
> * "select c from Lecturer l join l.course c"
> This happens ONLY if I run this stuff against Oracle. In MySQL it seems to
> work properly.
> I'll try to create a unit test for it.
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