Yun Tang created FLINK-18060:
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Summary: Add notice for heap-based state backend of state access
reference problem
Key: FLINK-18060
URL: https://issues.apache.org/jira/browse/FLINK-18060
Project: Flink
Issue Type: Bug
Components: Documentation
Reporter: Yun Tang
Currently, when talking about the limitation of {{MemoryStateBackend}} and
{{FsStateBackend}} in
[documentation|https://ci.apache.org/projects/flink/flink-docs-stable/ops/state/state_backends.html#the-memorystatebackend],
Flink only focus on the memory checkpoint size limit. However, current
documentation forgets to talk about the reference problem, which added in
{{CopyOnWriteStateMap}}:
{noformat}
IMPORTANT: the contracts for this class rely on the user not holding any
references to objects returned by this map beyond the life cycle of per-element
operations. Or phrased differently, all get-update-put operations on a mapping
should be within one call of processElement. Otherwise, the user must take care
of taking deep copies, e.g. for caching purposes.
{noformat}
This actually also applies to {{NestedStateMap}}.
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