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https://issues.apache.org/jira/browse/ARROW-398?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17657432#comment-17657432
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Rok Mihevc commented on ARROW-398:
----------------------------------
This issue has been migrated to [issue
#16026|https://github.com/apache/arrow/issues/16026] on GitHub. Please see the
[migration documentation|https://github.com/apache/arrow/issues/14542] for
further details.
> [Java] Java file format requires bitmaps of all 1's to be written when there
> are no nulls
> -----------------------------------------------------------------------------------------
>
> Key: ARROW-398
> URL: https://issues.apache.org/jira/browse/ARROW-398
> Project: Apache Arrow
> Issue Type: Bug
> Components: Java
> Reporter: Wes McKinney
> Assignee: Julien Le Dem
> Priority: Blocker
> Fix For: 0.2.0
>
>
> From the format specification "Arrays having a 0 null count may choose to not
> allocate the null bitmap. Implementations may choose to always allocate one
> anyway as a matter of convenience, but this should be noted when memory is
> being shared."
> When the null count is 0 and the validity buffer has length 0, then in Java
> for now the simplest thing will be to allocate a new validity buffer with all
> 1's. See the corresponding C++ logic where a 0-length buffer is being written
> when the null count is 0:
> https://github.com/apache/arrow/blob/master/cpp/src/arrow/ipc/adapter.cc#L83
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