[IcebergIO] CDC record and sort key

[ahmedabu98]

Part of #39979

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.33%. Comparing base (eea1e03) to head (1910d50).
⚠️ Report is 257 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #39981      +/-   ##
============================================
+ Coverage     55.95%   58.33%   +2.37%     
- Complexity     2272    13542   +11270     
============================================
  Files          1112     2566    +1454     
  Lines        175063   267300   +92237     
  Branches       1458    11054    +9596     
============================================
+ Hits          97959   155926   +57967     
- Misses        74645   105460   +30815     
- Partials       2459     5914    +3455     

Flag	Coverage Δ
java	64.57% <ø> (-11.07%)	⬇️

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[github-actions]

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R: @kennknowles for label java.

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[kennknowles]

Also, once you are "inside" a sink, you don't (necessarily) need the implicit propagation of ValueKind as metadata, since it is more like an explicit field you will write to the sink.

[kennknowles]

Is there any world in which Python will want to directly send these CdcRecord things over the wire? Just curious. You would want a StructuredCoder<CdcRecord> not a CustomCoder which I think translates to beam:coder:javasdk with java serialized payload, aka not intelligible to runners or other languages.

[ahmedabu98]

CdcRecord is something internal to the sink. The user supplies Beam Rows (whether it's Java or Python) and they they get resolved and converted to CdcRecords