[jira] [Assigned] (FLINK-6589) ListSerializer should deserialize as ArrayList with size + 1

["Fabian Hueske (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-6589?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Fabian Hueske reassigned FLINK-6589:
------------------------------------

    Assignee: Fabian Hueske

> 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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