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 78.57143% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.36%. Comparing base (6e68e20) to head (03afd40).
⚠️ Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
...oogle/cloud/teleport/v2/utils/DatastreamToDML.java	78.57%	3 Missing and 9 partials ⚠️

❌ Your patch check has failed because the patch coverage (78.57%) 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    #4232   +/-   ##
=========================================
  Coverage     56.35%   56.36%           
- Complexity     7858     7875   +17     
=========================================
  Files          1154     1154           
  Lines         73194    73270   +76     
  Branches       8580     8606   +26     
=========================================
+ Hits          41252    41295   +43     
- Misses        29158    29177   +19     
- Partials       2784     2798   +14     

Components	Coverage Δ
spanner-templates	84.48% <ø> (+<0.01%)	⬆️
spanner-import-export	68.91% <ø> (-0.15%)	⬇️
spanner-live-forward-migration	88.99% <ø> (+0.01%)	⬆️
spanner-live-reverse-replication	80.87% <ø> (+0.01%)	⬆️
spanner-bulk-migration	89.00% <ø> (+<0.01%)	⬆️
gcs-spanner-dv	88.11% <ø> (+0.01%)	⬆️

Files with missing lines	Coverage Δ
...oogle/cloud/teleport/v2/utils/DatastreamToDML.java	44.35% <78.57%> (+9.48%)	⬆️

... and 13 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.