[jira] [Commented] (ARROW-10970) [Rust][DataFusion] Implement Value(Null)

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

    [ https://issues.apache.org/jira/browse/ARROW-10970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17252294#comment-17252294 ] 

Mike Seddon commented on ARROW-10970:
-------------------------------------

Added as part of https://github.com/apache/arrow/pull/8966

For future reference:

I have now added the NULL value to both the test cases and the planner.

This is where things get interesting. For this statement:

SELECT NULL

Spark implements a special NullType for this return type but that creates a lot of side effects for things like the Parquet writer and JDBC drivers do not support this type.

I tested Postgres:

CREATE TABLE test AS
SELECT NULL;

The DDL for this table shows that column as a text type so that is why I have applied the default utf8 type to Value(Null).

> [Rust][DataFusion] Implement Value(Null)
> ----------------------------------------
>
>                 Key: ARROW-10970
>                 URL: https://issues.apache.org/jira/browse/ARROW-10970
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Rust - DataFusion
>            Reporter: Mike Seddon
>            Priority: Major
>
> We need to add support for the NULL value. 
> For example:
> ```sql
> SELECT char_length(NULL) AS char_length_null
> ```



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