Support custom avro DatumReader when reading from BigQuery

[kkdoon]

Similar to 11479 this PR adds functionality to directly deserialize Avro records to the target class, via the user specified DatumReader, in BigQueryIO.

R: @pabloem @chamikaramj @steveniemitz

This fixes #22717

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[steveniemitz]

can we plumb this down into BigQueryStorageAvroReader as well so it'll work with direct reads?

[steveniemitz]

can we make the reader schema optional, and use the writer schema if its not set? Thats how AvroIO works IIRC.

[kkdoon]

It seems like AvroIO derives it in case the class is of SpecificData subType. We could do the same but we would need to take the class type as input instead (don't think its cleaner though).

Also, readerSchema is needed by AvroSource in general, as it does validation based on that, if parserFn is not set,
as well as derives the AvroCoder based on the readerSchema. Since it gets the writer schema during runtime from the file metadata, we cannot assign reader schema as writer schema on the submitter side.

[kkdoon]

BigQueryStorageAvroReader

yeah, i was thinking of tackling that in another review. I could add in this one too to allow this for different read types.

[steveniemitz]

BigQueryStorageAvroReader

yeah, i was thinking of tackling that in another review. I could add in this one too to allow this for different read types.

that's cool, you can do it in another review, just curious.

[github-actions]

Reminder, please take a look at this pr: @kennknowles @chamikaramj

[kennknowles]

R: @chamikaramj

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[steveniemitz]

Run Java PreCommit

[steveniemitz]

Run Java PreCommit

[steveniemitz]

Run Java_Examples_Dataflow PreCommit

[steveniemitz]

Run Java_Examples_Dataflow_Java11 PreCommit

[steveniemitz]

Run Java_Examples_Dataflow_Java17 PreCommit

[steveniemitz]

Run Java PreCommit

[steveniemitz]

Run Java PreCommit

[kkdoon]

I ran and profiled a few dataflow jobs with and without my changes to test for performance regression. Overall the profiling data looks good for these new changes.

[ahmedabu98]

I believe this PR broke Java Dataflow PostCommits: https://ci-beam.apache.org/job/beam_PostCommit_Java_DataflowV1/2173/testReport/. See #23541