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https://issues.apache.org/jira/browse/FLINK-33183?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17771876#comment-17771876
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Timo Walther commented on FLINK-33183:
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[~lincoln.86xy] what is you opinion here? This might be more controversial than 
FLINK-33182. But I think that the behavior actually depends on VIRTUAL vs 
non-VIRTUAL in order to cause issues.

> Enable metadata columns in NduAnalyzer with retract if non-virtual
> ------------------------------------------------------------------
>
>                 Key: FLINK-33183
>                 URL: https://issues.apache.org/jira/browse/FLINK-33183
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table SQL / Planner
>            Reporter: Timo Walther
>            Priority: Major
>
> Currently, the NduAnalyzer is very strict about metadata columns in updating 
> sources. Compared to append and upsert sources (see also FLINK-33182), 
> retract sources are tricky. And the analyzer is actually correct.
> However, for retract sources we should expose more functionality to the user 
> and add a warning to the documentation that retract mode could potentially 
> cause NDU problems if not enough attention is paid. We should only throw an 
> error on virtual metadata columns. Persisted metadata columns can be 
> considered “safe“. When a metadata column is persisted, we can assume that an 
> upstream Flink job fills its content thus likely also fills its correct 
> retraction.



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