Kenneth Knowles created BEAM-6906:
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Summary: Mutating accumulators in fused stages is generally unsafe
- need to provide a single mutable accumulator
Key: BEAM-6906
URL: https://issues.apache.org/jira/browse/BEAM-6906
Project: Beam
Issue Type: Test
Components: beam-model
Reporter: Kenneth Knowles
Assignee: Yueyang Qiu
Our current docs encourage a CombineFn author to mutate accumulators for
efficiency. This is important, but cannot be done generally without losing
efficiency - it is not safe to share accumulators within a stage or across
sliding windows. The ownership story needs to be clear. Any accumulator that is
mutable is from that point on owned by the CombineFn, not the runner and cannot
be given to other steps.
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