feat(datastream-to-SQL): Support DELETE replication for tables without Primary Keys using ROWID

[yonatandt]

• Fix regression in DatastreamToDML where tables lacking primary keys produced empty WHERE clauses for DELETE events.
• Add ROWID fallback in getPrimaryKeyToValueFilterSql when primaryKeys is empty or unmapped.
• Allow getDmlTemplate to generate DELETE DML when rowid or _metadata_row_id is present.
• Make DatastreamRow getPrimaryKeys and getStringValue null-safe against missing metadata fields.
• Add unit tests verifying ROWID fallback in DatastreamToDMLTest and DatastreamRowTest.

Fixes b/506993545

[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 addresses a regression in the DatastreamToDML component where DELETE events for tables without primary keys were failing due to empty WHERE clauses. By implementing a ROWID fallback mechanism, the system can now correctly identify and process these deletions. Additionally, the changes improve the robustness of metadata field handling within DatastreamRow to ensure more reliable data processing.

Highlights

• ROWID Support for DELETE: Added support for using ROWID as a fallback identifier for DELETE operations on tables that lack primary keys.
• Null-Safety Improvements: Enhanced DatastreamRow to be null-safe when accessing metadata fields, preventing potential crashes during record processing.
• Unit Testing: Introduced comprehensive unit tests in DatastreamToDMLTest and DatastreamRowTest to verify the new ROWID fallback logic and null-safety fixes.

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[codecov]

Codecov Report

❌ Patch coverage is 86.27451% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.89%. Comparing base (39361e9) to head (255c22e).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...oogle/cloud/teleport/v2/utils/DatastreamToDML.java	83.72%	0 Missing and 7 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4232      +/-   ##
============================================
+ Coverage     55.86%   55.89%   +0.03%     
- Complexity     7490     7507      +17     
============================================
  Files          1135     1135              
  Lines         70313    70357      +44     
  Branches       8040     8061      +21     
============================================
+ Hits          39282    39329      +47     
+ Misses        28480    28472       -8     
- Partials       2551     2556       +5     

Components	Coverage Δ
spanner-templates	84.20% <ø> (ø)
spanner-import-export	69.01% <ø> (-0.02%)	⬇️
spanner-live-forward-migration	88.65% <ø> (ø)
spanner-live-reverse-replication	80.36% <ø> (ø)
spanner-bulk-migration	89.06% <ø> (ø)
gcs-spanner-dv	87.98% <ø> (ø)

Files with missing lines	Coverage Δ
...d/teleport/v2/datastream/values/DatastreamRow.java	50.00% <100.00%> (+11.42%)	⬆️
...oogle/cloud/teleport/v2/utils/DatastreamToDML.java	42.44% <83.72%> (+7.57%)	⬆️

... and 4 files with indirect coverage changes

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[gemini-code-assist]

Code Review

This pull request introduces null-safety improvements in DatastreamRow when parsing JSON fields and primary keys, and adds fallback support for row IDs (rowid or _metadata_row_id) when generating DML templates and filters in DatastreamToDML for tables without primary keys. The feedback recommends handling column casing in the row ID fallback logic of getValueSql to prevent issues when casing rules are applied, and refactoring the primary key extraction in DatastreamRow to avoid redundant JSON node lookups.