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https://issues.apache.org/jira/browse/BEAM-2595?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ahmet Altay resolved BEAM-2595.
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Resolution: Fixed
> WriteToBigQuery does not work with nested json schema
> -----------------------------------------------------
>
> Key: BEAM-2595
> URL: https://issues.apache.org/jira/browse/BEAM-2595
> Project: Beam
> Issue Type: Bug
> Components: sdk-py
> Affects Versions: 2.1.0
> Environment: mac os local runner, Python
> Reporter: Andrea Pierleoni
> Assignee: Sourabh Bajaj
> Priority: Minor
> Labels: gcp
> Fix For: 2.1.0
>
>
> I am trying to use the new `WriteToBigQuery` PTransform added to
> `apache_beam.io.gcp.bigquery` in version 2.1.0-RC1
> I need to write to a bigquery table with nested fields.
> The only way to specify nested schemas in bigquery is with teh json schema.
> None of the classes in `apache_beam.io.gcp.bigquery` are able to parse the
> json schema, but they accept a schema as an instance of the class
> `apache_beam.io.gcp.internal.clients.bigquery.TableFieldSchema`
> I am composing the `TableFieldSchema` as suggested here
> [https://stackoverflow.com/questions/36127537/json-table-schema-to-bigquery-tableschema-for-bigquerysink/45039436#45039436],
> and it looks fine when passed to the PTransform `WriteToBigQuery`.
> The problem is that the base class `PTransformWithSideInputs` try to pickle
> and unpickle the function
> [https://github.com/apache/beam/blob/master/sdks/python/apache_beam/transforms/ptransform.py#L515]
> (that includes the TableFieldSchema instance) and for some reason when the
> class is unpickled some `FieldList` instance are converted to simple lists,
> and the pickling validation fails.
> Would it be possible to extend the test coverage to nested json objects for
> bigquery?
> They are also relatively easy to parse into a TableFieldSchema.
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