[jira] [Commented] (SPARK-38227) Apply strict nullability of nested column in time window / session window

["Jungtaek Lim (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-38227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17493104#comment-17493104 ] 

Jungtaek Lim commented on SPARK-38227:
--------------------------------------

Will submit a PR sooner.

> Apply strict nullability of nested column in time window / session window
> -------------------------------------------------------------------------
>
>                 Key: SPARK-38227
>                 URL: https://issues.apache.org/jira/browse/SPARK-38227
>             Project: Spark
>          Issue Type: Bug
>          Components: Structured Streaming
>    Affects Versions: 3.2.1, 3.3.0
>            Reporter: Jungtaek Lim
>            Priority: Major
>
> In TimeWindow and SessionWindow, we define dataType of these function expressions as StructType having two nested columns "start" and "end", which is "nullable".
> And we replace these expressions in the analyzer via corresponding rules, TimeWindowing for TimeWindow, and SessionWindowing for SessionWindow.
> The rules replace the function expressions with Alias, referring CreateNamedStruct. For the value side of CreateNamedStruct, we don't specify anything about nullability, which leads to a risk the value side may be interpreted (or optimized) as non-nullable, which would be different Spark would be expected.
> We should make sure the nullability of columns in CreateNamedStruct remains the same with dataType definition on these function expressions.



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