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https://issues.apache.org/jira/browse/SPARK-27424?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dongjoon Hyun updated SPARK-27424:
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Affects Version/s: (was: 3.0.0)
3.1.0
> Joining of one stream against the most recent update in another stream
> ----------------------------------------------------------------------
>
> Key: SPARK-27424
> URL: https://issues.apache.org/jira/browse/SPARK-27424
> Project: Spark
> Issue Type: Improvement
> Components: Structured Streaming
> Affects Versions: 3.1.0
> Reporter: Thilo Schneider
> Priority: Major
> Attachments: join-last-update-design.pdf
>
>
> Currently, adding the most recent update of a row with a given key to another
> stream is not possible. This situation arises if one wants to use the current
> state, of one object, for example when joining the room temperature with the
> current weather.
> This ticket covers creation of a {{stream_lead}} and modification of the
> streaming join logic (and state store) to additionally allow joins of the
> form
> {code:sql}
> SELECT *
> FROM A, B
> WHERE
> A.key = B.key
> AND A.time >= B.time
> AND A.time < stream_lead(B.time)
> {code}
> The major aspect of this change is that we actually need a third watermark to
> cover how late updates may come.
> A rough sketch may be found in the attached document.
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