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https://issues.apache.org/jira/browse/ARROW-12293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17332404#comment-17332404
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Andrew Lamb commented on ARROW-12293:
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Migrated to github: https://github.com/apache/arrow-datafusion/issues/197
> [Rust][DataFusion] Word Count
> -----------------------------
>
> Key: ARROW-12293
> URL: https://issues.apache.org/jira/browse/ARROW-12293
> Project: Apache Arrow
> Issue Type: Wish
> Components: Rust - DataFusion
> Reporter: Jacob Baumbach
> Priority: Trivial
> Labels: newbie, question
>
> I am learning DataFusion and tried to do the canonical big data version of
> hello world, word count, using DataFusion. I have been unsuccessful, and I
> am wondering if word count is even currently possible with DataFusion.
>
> Typically word count involves a flat_map where you split each string based on
> the white space contained within each string.
>
> There are two issues I am running into
> 1) creating a udf that goes from &str -> Vec<&str>. I cannot find an
> `arrow::array` that maps to a collection of string, which is preventing me
> from creating a udf that can perform the split.
> 2) Assuming I could get `1` to work, I am not aware of a method that is
> similar to flat_map that may be performed on a column. In sql, I believe
> this is called `explode`, which I can't find in the codebase, which makes me
> think flat_map style operations aren't possible.
>
> My questions are:
> Is word count currently possible in DataFusion? If so, how can perform the
> split and how can you perform a flat_map? If word count cannot be done, what
> would need to be implemented to make it possible?
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