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https://issues.apache.org/jira/browse/ARROW-13467?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17476403#comment-17476403
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Ian Cook commented on ARROW-13467:
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See this thread from the user@ list for more details and notes on a possible
resolution: https://lists.apache.org/thread/ygzc8gj5nv7453wwg4k0g0d9pl51qs2l
> [C++] Support delta dictionaries in the IPC file format
> -------------------------------------------------------
>
> Key: ARROW-13467
> URL: https://issues.apache.org/jira/browse/ARROW-13467
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Weston Pace
> Priority: Major
>
> The spec states:
> > In the file format, there is no requirement that dictionary keys should be
> > defined in a
> > {{DictionaryBatch}} before they are used in a {{RecordBatch}}, as long as
> > the keys are
> > defined somewhere in the file. Further more, it is invalid to have more
> > than one *non-delta*
> > dictionary batch per dictionary ID (i.e. dictionary replacement is not
> > supported). Delta
> > dictionaries are applied in the order they appear in the file footer.
> This seems to suggest that dictionary deltas (but not replacements) are
> allowed. However, both reading and writing an IPC file with a dictionary
> delta fails.
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