ARROW-10508 [Java] Allow FixedSizeListVector to have empty children

[Kopilov]

Hope this would be enough

[github-actions]

https://issues.apache.org/jira/browse/ARROW-10508

[liyafan82]

Maybe we can add a case to insert null into the vector?

[Kopilov]

@liyafan82 good idea, added test case to PR.
Also tested together with C++ in my demo project: commit, workflow.
Everything looks like OK

[liyafan82]

@liyafan82 good idea, added test case to PR.
Also tested together with C++ in my demo project: commit, workflow.
Everything looks like OK

@Kopilov Thanks for your follow-up.

The new test case testVectorWithNulls is nice to have.
What I meant was that maybe we need a null slot in the list vector, and test our vector correctly distinguishes between an empty array and a null (sorry I did not made this clear enough)
I've prepared a commit for that. Could you please check?

[Kopilov]

@liyafan82 seems working correctly in all cases if we add writer.startList and writer.endList together with vector.setNull.
I have refactored writeListVector function in test to make it more universal.

May be we should add a getter for protected FixedSizeListVector vector prorerty in UnionFixedSizeListWriter and/or cache FixedSizeListVector.getWriter output (in current version new writer is created on every invocation). This allows writeListVector ans similar methods to have only vector or only writer parameter with keeping new functional.

Cross-test with C++ is again made in my project. But where are cross tests made in Apache Arrow itself?

[liyafan82]

@liyafan82 seems working correctly in all cases if we add writer.startList and writer.endList together with vector.setNull.
I have refactored writeListVector function in test to make it more universal.

May be we should add a getter for protected FixedSizeListVector vector prorerty in UnionFixedSizeListWriter and/or cache FixedSizeListVector.getWriter output (in current version new writer is created on every invocation). This allows writeListVector ans similar methods to have only vector or only writer parameter with keeping new functional.

Cross-test with C++ is again made in my project. But where are cross tests made in Apache Arrow itself?

@Kopilov Thanks for your effort. It looks reasonable. Will merge soon if there are no more comments.

Concerning the problem of caching writers, maybe you can open a separate JIRA for it, if you think it necessary.

We have integeration tests across different languages in "Integration / AMD64 Conda Integration Test (pull_request)" when a PR is submitted.

[liyafan82]

Merging. Thanks for your effort. @Kopilov