[jira] [Commented] (ARROW-11851) [Rust][DataFusion] Add coercion support for `NULL` literals

["Mike Seddon (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-11851?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17294845#comment-17294845 ] 

Mike Seddon commented on ARROW-11851:
-------------------------------------

[~alamb] Previously I implemented the Null=UTF8 type based on the behavior of Postgres not Spark - because the Spark implementation comes with a lot of side effects like the fact that Parquet does not support the `NullType`. We can revisit.

> [Rust][DataFusion] Add coercion support for `NULL` literals
> -----------------------------------------------------------
>
>                 Key: ARROW-11851
>                 URL: https://issues.apache.org/jira/browse/ARROW-11851
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Rust - DataFusion
>            Reporter: Andrew Lamb
>            Priority: Major
>
> As we observed in https://github.com/apache/arrow/pull/9565#discussion_r586347165 datafusion won't coerce null literals, forcing strange syntax such as:
> ```
> rpad('hi', CAST(NULL AS INT), 'xy')
> We should add automatic coercion logic from the null literal to any type and this expression should work just fine (produce a NULL output)
> ```
> rpad('hi', NULL, 'xy')
> ```



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