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

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

Fabian Hueske created FLINK-6589:
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             Summary: 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


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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