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https://issues.apache.org/jira/browse/SPARK-42376?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-42376:
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    Assignee:     (was: Apache Spark)

> Introduce watermark propagation among operators
> -----------------------------------------------
>
>                 Key: SPARK-42376
>                 URL: https://issues.apache.org/jira/browse/SPARK-42376
>             Project: Spark
>          Issue Type: Improvement
>          Components: Structured Streaming
>    Affects Versions: 3.5.0
>            Reporter: Jungtaek Lim
>            Priority: Major
>
> With introduction of SPARK-40925, we enabled workloads containing multiple 
> stateful operators in a single streaming query.
> The JIRA ticket clearly described out-of-scope, "Here we propose fixing the 
> late record filtering in stateful operators to allow chaining of stateful 
> operators {*}which do not produce delayed records (like time-interval join or 
> potentially flatMapGroupsWithState){*}".
> We identified production use case for stream-stream time-interval join 
> followed by stateful operator (e.g. window aggregation), and propose to 
> address such use case via this ticket.
> The design will be described in the PR, but the sketched idea is introducing 
> simulation of watermark propagation among operators. As of now, Spark 
> considers all stateful operators to have same input watermark and output 
> watermark, which introduced the limitation. With this ticket, we construct 
> the logic to simulate watermark propagation so that each operator can have 
> its own (input watermark, output watermark). Operators introducing delayed 
> records will produce delayed output watermark, and downstream operator can 
> take the delay into account as input watermark will be adjusted.



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