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https://issues.apache.org/jira/browse/BEAM-839?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Groh resolved BEAM-839.
------------------------------
Resolution: Fixed
Fix Version/s: 0.4.0-incubating
This was linear time (with regards to the number of keys) update in
{{WatermarkManager}}. It has been replaced with an O(log n) update.
> The DirectRunner slows down significantly as the number of keys increases
> -------------------------------------------------------------------------
>
> Key: BEAM-839
> URL: https://issues.apache.org/jira/browse/BEAM-839
> Project: Beam
> Issue Type: Bug
> Reporter: Thomas Groh
> Assignee: Thomas Groh
> Fix For: 0.4.0-incubating
>
>
> For example, running WordCount on KingLear takes approximately 10 seconds,
> while running WordCount on all of Shakespeare takes approximately 5 minutes.
> The primary cost is maintaining a PriorityQueue of Watermark Holds, which
> takes {{O(n**2)}} time, where {{n}} is the number of keys at a step.
> Additionally, there are two other things that cause slowness. The first is
> use of UUID.randomUUID in the constructor of DelegatingAggregator, which uses
> a shared SecureRandom, which synchronizes on call to {{nextBytes(byte[])}}
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