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From "Vikas Kedigehalli (JIRA)" <>
Subject [jira] [Commented] (BEAM-1956) Flatten operation should respect input type hints.
Date Thu, 20 Apr 2017 20:16:04 GMT


Vikas Kedigehalli commented on BEAM-1956:

The fix is a workaround for the dataflow runner limitations
but underlying issue still remains (see the description of this jira)

> Flatten operation should respect input type hints.
> --------------------------------------------------
>                 Key: BEAM-1956
>                 URL:
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-py
>            Reporter: Vikas Kedigehalli
>            Assignee: Ahmet Altay
>             Fix For: First stable release
> Input type hints are currently not respected by the Flatten operation and instead `Any`
type is chosen as a fallback. This could lead to using a pickle coder even if there was a
custom coder type hint provided for input PCollections. 
> Also, this could lead to undesirable results, particularly, when a Flatten operation
is followed by a GroupByKey operation which requires the key coder to be deterministic. Even
if the user provides deterministic coder type hints to their PCollections, defaulting to Any
would result in using the pickle coder (non-deterministic). As a result of this, CoGroupByKey
is broken in such scenarios where input PCollection coder is deterministic for the type while
pickle coder is not.   

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