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https://issues.apache.org/jira/browse/FLINK-6589?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16013760#comment-16013760
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ASF GitHub Bot commented on FLINK-6589:
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Github user StefanRRichter commented on the issue:
https://github.com/apache/flink/pull/3912
Yes, there is a tradeoff, and probably the nicest way would be to restore
the internal array size as it was when we serialized the original. However, I
guess that is too much effort for the effect. Since the sweetspot also depends
on the access pattern, I think everything from +1 to some percentage could be
justified and as there is no clear "best strategy" I would leave this up to
your judgment call.
+1 from me then.
> ListSerializer should deserialize as ArrayList with size + 1
> ------------------------------------------------------------
>
> Key: FLINK-6589
> URL: https://issues.apache.org/jira/browse/FLINK-6589
> Project: Flink
> Issue Type: Improvement
> Components: Core
> Affects Versions: 1.3.0, 1.4.0
> Reporter: Fabian Hueske
> Assignee: Fabian Hueske
>
> The {{ListSerializer}} deserializes a list as {{ArrayList}} with exactly the
> required capacity, i.e., number of serialized objects.
> Several operators in the Table API have a {{MapState<Long, List<X>>}} to
> store received elements in a list per timestamp. Hence, retrieving the list
> and adding one element to the list is a very common operation.
> Since the list which is deserialized has no room left for adding elements,
> the first insertion into the list will result in growing the {{ArrayList}}
> which is expensive.
> I propose to initialize the {{ArrayList}} returned by the {{ListSerializer}}
> with numberOfSerializedElements + 1. This will only marginally increase the
> size of the list and allow for one insertion without growing the list.
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