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https://issues.apache.org/jira/browse/CAY-2792?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17685373#comment-17685373
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Matt Watson commented on CAY-2792:
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[~ntimofeev] I tried that exact fix at first. It allowed my breaking test to
pass, however it caused 5 other tests within {{cayenne-server}} to fail, all
were throwing the {{{}ConcurrentModificationException{}}}.
The reason my test passes is because [ChildReflexive, ParentReflexive, Other]
will sort the {{subList}} on the final iteration, so it doesn't
{{{}checkForComodification{}}}. But, it looks like other cayenne-server tests
will have more mixed Entites, and attempt to sort previously encountered
records when it still has more iterations to execute.
So maybe doing just that same change and changing the for each loop to a {{for
i}} loop will solve the {{{}ConcurrentModificationException{}}}. I will try
that now.
> Fix Insertion Order For Reflexive DataObjects
> ---------------------------------------------
>
> Key: CAY-2792
> URL: https://issues.apache.org/jira/browse/CAY-2792
> Project: Cayenne
> Issue Type: Bug
> Components: Core Library
> Affects Versions: 4.2.RC2, 4.2.RC1
> Environment: Java 17
> Reporter: Matt Watson
> Assignee: Nikita Timofeev
> Priority: Critical
> Fix For: 4.2, 5.0.M1
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> For terminology's sake, I assume _Reflexive_ refers to when you have 2
> objects of the same Model, that are related, in this case, parent/child
> (ToOne/HasMany). If this assumption is incorrect we can rename the title.
> For a little history on this, we never encountered this bug until we upgraded
> to {{4.2.RC1}}, and I recently tested on {{4.2.RC2}} and the bug still exists.
> For a while I thought this was only a bug in our environment, thinking that
> our code was causing the issue because Cayenne has a passing test in
> {{CayenneDataObjectRelationshipsIT.testReflexiveRelationshipInsertOrder1}}.
> But as I got to digging, the error occurs when the parent also has a
> relationship to some "Other" object that is not of the same model.
> The [pull request|https://github.com/apache/cayenne/pull/563] has a breaking
> test. I have not worked on a fix yet, but will begin investigating. I suspect
> it has to do with the work done in CAY-2571, but I am not certain yet.
> The issue is that Cayenne randomly tries to commit the child record in front
> of the parent record, therefore the database throws a Foreign Key error,
> since the parent does not yet exist when the child is inserted. Because of
> this randomness, my breaking test attempts this process 100 times. You will
> also see another test that passes with the same Models but without setting
> the "ToOne" Other object.
> here is a look at the code that "randomly" fails:
> {code:java}
> public void addReflexiveParentAndChildWithOtherRelationshipOnParent() {
> // can add Reflexive Parent (that belongsTo Other) and Child,
> // we will do this 100 times, because it randomly does it
> correctly/incorrectly
> // given some "other" Object
> final Other other = context.newObject(Other.class);
> other.setName("OtherB");
> context.commitChanges();
> final int attempts = 100;
> int errors = 0;
> for (int i = 0; i < attempts; i++) {
> // when parent is created and associated to "Other"
> final Reflexive parent = context.newObject(Reflexive.class);
> parent.setName("parentB"+i);
> parent.setToOther(other);
> // and child is created and associated to "Parent"
> final Reflexive child = context.newObject(Reflexive.class);
> child.setName("childB"+i);
> child.setToParent(parent);
> try {
> context.commitChanges();
> } catch (final Exception e) {
> errors++;
> e.printStackTrace();
> context.rollbackChanges();
> }
> }
> // then no error occurred
> assertEquals(String.format("Failed on %s of %s attempts.", errors,
> attempts), 0, errors);
> }
> {code}
>
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