[jira] [Created] (BEAM-527) Pickling error when pickling a nested function

["Ahmet Altay (JIRA)" <ji...@apache.org>]

Ahmet Altay created BEAM-527:
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             Summary: Pickling error when pickling a nested function 
                 Key: BEAM-527
                 URL: https://issues.apache.org/jira/browse/BEAM-527
             Project: Beam
          Issue Type: Bug
          Components: sdk-py
            Reporter: Ahmet Altay
            Priority: Minor


There is a pickling error under the following conditions all happen:
- a function is defined inside a transforms' apply method
- then using it as MapFn
- that function references an instance variable of the outer transform.

Rewriting the nested function as an unnested DoFn appears to solve the problem.

If the limitations of pickling make it difficult to support nested functions then perhaps there's a way to make it easier for users to detect problems caused by nested functions and recommend appropriate fixes



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