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https://issues.apache.org/jira/browse/FLINK-3581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15266754#comment-15266754
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ASF GitHub Bot commented on FLINK-3581:
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Github user aljoscha commented on the pull request:
https://github.com/apache/flink/pull/1957#issuecomment-216261831
I had a version that was doing this. The problem there is that you don't
know when you can drop column families. For knowing when a column family is
empty you would have to keep a Set of keys for which you have state in memory.
Which somewhat defeats the purpose of the RocksDB backend.
> Add Special Aligned Event-Time WindowOperator
> ---------------------------------------------
>
> Key: FLINK-3581
> URL: https://issues.apache.org/jira/browse/FLINK-3581
> Project: Flink
> Issue Type: Improvement
> Components: Streaming
> Reporter: Aljoscha Krettek
> Assignee: Aljoscha Krettek
>
> The current Window Trigger is per key. Meaning every window has a (logical)
> Trigger for every key in the window, i.e. there will be state and time
> triggers per key per window.
> For some types of windows, i.e. based on time it is possible to use a single
> Trigger to fire for all keys at the same time. In that case we would save a
> lot of space on state and timers. Which makes state snapshots a lot smaller.
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