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https://issues.apache.org/jira/browse/BEAM-1956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15969521#comment-15969521
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ASF GitHub Bot commented on BEAM-1956:
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GitHub user vikkyrk opened a pull request:
https://github.com/apache/beam/pull/2543
[BEAM-1956] Modify types for input PCollections of Flatten transform
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---
Modify types for input PCollections of Flatten transform to that of the
output PCollection
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/vikkyrk/incubator-beam py_flatten_visitor
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/beam/pull/2543.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #2543
----
commit e3ac1f4d3298b2e32463b6b132dda89706a6bc58
Author: Vikas Kedigehalli <[email protected]>
Date: 2017-04-14T20:53:13Z
Modifying types for input PCollectios of Flatten transform with that of the
output PCollection
----
> Flatten operation should respect input type hints.
> --------------------------------------------------
>
> Key: BEAM-1956
> URL: https://issues.apache.org/jira/browse/BEAM-1956
> Project: Beam
> Issue Type: Bug
> Components: sdk-py
> Reporter: Vikas Kedigehalli
> Assignee: Vikas Kedigehalli
> 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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