fix(datastream-to-bigquery): Added support to read SQLServer Primary keys from replication_index to support Merge operation (Issue #3805)

[sandesh-jagdale-tp]

This is to address the correct reading of SQL Server primary keys from "replication_index" metadata field, if the primary key is not found in the default metadata field "primary_keys".

This is to address the issue reported in the bug - #3805

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a fallback mechanism for identifying primary keys in Datastream records. By checking the 'replication_index' metadata field when 'primary_keys' is unavailable, the system now correctly supports SQL Server CDC sources, enabling proper Merge operations in BigQuery.

Highlights

• Primary Key Resolution: Updated the primary key extraction logic to prioritize the 'primary_keys' field while falling back to 'replication_index' for SQL Server sources.
• Enhanced Test Coverage: Added comprehensive unit tests to verify the fallback mechanism and ensure correct behavior when both fields are present or absent.

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[gemini-code-assist]

Code Review

This pull request introduces a fallback mechanism for retrieving primary keys from Datastream metadata, specifically adding support for 'replication_index' when 'primary_keys' is absent. The changes update both 'FormatDatastreamJsonToJson' and 'FormatDatastreamRecordToJson' classes and include comprehensive unit tests to verify the new logic. The review identified a potential NullPointerException risk and performance concerns in 'FormatDatastreamRecordToJson', as well as a need to handle explicitly null JSON nodes in 'FormatDatastreamJsonToJson' to ensure the fallback logic functions correctly.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.65%. Comparing base (0025d7e) to head (0f8e7c8).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...tream/transforms/FormatDatastreamRecordToJson.java	62.50%	0 Missing and 3 partials ⚠️
...astream/transforms/FormatDatastreamJsonToJson.java	71.42%	0 Missing and 2 partials ⚠️

❌ Your patch check has failed because the patch coverage (66.66%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3806      +/-   ##
============================================
+ Coverage     53.62%   53.65%   +0.02%     
- Complexity     6323     6736     +413     
============================================
  Files          1087     1087              
  Lines         66762    66772      +10     
  Branches       7476     7481       +5     
============================================
+ Hits          35801    35826      +25     
+ Misses        28534    28518      -16     
- Partials       2427     2428       +1     

Components	Coverage Δ
spanner-templates	72.83% <ø> (+0.03%)	⬆️
spanner-import-export	68.64% <ø> (+0.11%)	⬆️
spanner-live-forward-migration	80.93% <ø> (-0.02%)	⬇️
spanner-live-reverse-replication	77.08% <ø> (-0.02%)	⬇️
spanner-bulk-migration	91.10% <ø> (-0.01%)	⬇️
gcs-spanner-dv	85.74% <ø> (-0.02%)	⬇️

Files with missing lines	Coverage Δ
...astream/transforms/FormatDatastreamJsonToJson.java	57.35% <71.42%> (+1.96%)	⬆️
...tream/transforms/FormatDatastreamRecordToJson.java	53.10% <62.50%> (+1.67%)	⬆️

... and 7 files with indirect coverage changes

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