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https://issues.apache.org/jira/browse/FLINK-5710?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15856358#comment-15856358
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Fabian Hueske commented on FLINK-5710:
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The idea is to kind of apply pattern matching for certain expressions such as
{{GROUP BY FLOOR(procTime() TO HOURS)}}.
The challenge is that this expression is spread across several LogicalRel nodes.
The expression {{FLOOR(procTime() TO HOURS)}} will be moved into a
{{LogicalProject}} (or {{LogicalCalc}}) to create a new attribute. A following
{{LogicalAggregate}} will then use that attribute as a grouping column.
Once we detect such a pattern, we have to rewrite the plan and replace the
{{LogicalAggregate}} and parts of the {{LogicalProject}} by a
{{LogicalWindowAggregate}}. The {{LogicalWindowAggregate}} includes a window
definition. Depending on which marker function is used ({{rowtime}} or
{{proctime}}) the window definition is either for a processing or an event time
window. After the translation, the function is no longer available.
With this approach, we can only translate very specific queries. However, I
don't think we can easily provide a generic translation for SQL window queries.
> Add ProcTime() function to indicate StreamSQL
> ---------------------------------------------
>
> Key: FLINK-5710
> URL: https://issues.apache.org/jira/browse/FLINK-5710
> Project: Flink
> Issue Type: New Feature
> Components: DataStream API
> Reporter: Stefano Bortoli
> Assignee: Stefano Bortoli
> Priority: Minor
>
> procTime() is a parameterless scalar function that just indicates processing
> time mode
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