feat: Add file name metadata column to parquet reading.

[emkornfield]

🥞 Stacked PR

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• stack/add_file_metadata [Files changed]

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This adds a file name metadata column, to be able to determine which file a particular row came from. It also documents RowIndex as a requirement for Parquet readers.

TESTING=Added a new unit test.

[codecov]

Codecov Report

❌ Patch coverage is 82.03125% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.74%. Comparing base (ac8510e) to head (e8842b7).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
kernel/src/engine/default/parquet.rs	38.46%	7 Missing and 1 partial ⚠️
kernel/src/engine/arrow_utils.rs	92.30%	0 Missing and 7 partials ⚠️
kernel/src/schema/mod.rs	55.55%	4 Missing ⚠️
kernel/src/scan/state_info.rs	0.00%	3 Missing ⚠️
kernel/src/engine/sync/parquet.rs	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1512      +/-   ##
==========================================
+ Coverage   84.67%   84.74%   +0.07%     
==========================================
  Files         122      122              
  Lines       32741    33188     +447     
  Branches    32741    33188     +447     
==========================================
+ Hits        27722    28126     +404     
- Misses       3674     3678       +4     
- Partials     1345     1384      +39     

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[emkornfield]

this might not be strictly necessary, but seems reasonable as a step towards iceberg unification.

[nicklan]

Seems good to me. One odd thing is that we call it the "filename" column, but it's really the "file path" column. Is that an issue or is this already something common in parquet that I just don't know about

[nicklan]

at some point we should probably agree on what we want to call these :)

[emkornfield]

Naming was taken from iceberg spec, but I agree FilePath for the variable name is better lets do that.

[emkornfield]

renamed to FilePath, happy to change this for now, just seemed a cheap way to be consistent but not too important, let me know if you prefer "file_path"