Fabian Hueske created FLINK-5151:
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Summary: Add discussion about object mutations to heap-based state
backend docs.
Key: FLINK-5151
URL: https://issues.apache.org/jira/browse/FLINK-5151
Project: Flink
Issue Type: Improvement
Components: Documentation
Affects Versions: 1.2.0, 1.1.4
Reporter: Fabian Hueske
Flink's heap state backends store data as objects on the heap. Any object
mutations are hence reflected in the state.
This can lead to unexpected behavior. For example, in case of sliding windows,
multiple window hold references to the same object. Hence, all windows are
affected if such an object is modified, e.g., by a {{WindowFunction}},
{{ReduceFunction}}, or {{FoldFunction}}, and might return invalid results.
We should add this information to the state backend documentation and also
point out that the RocksDB backend is not affected by this because all data is
serialized.
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