draft: feat: use shape touched information in necessary columns optimization

[douglasdavis]

No description provided.

[codecov-commenter]

Codecov Report

Merging #368 (8ad6643) into main (e8403c5) will increase coverage by 0.07%.
The diff coverage is 91.66%.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

@@            Coverage Diff             @@
##             main     #368      +/-   ##
==========================================
+ Coverage   93.81%   93.89%   +0.07%     
==========================================
  Files          23       23              
  Lines        2925     2930       +5     
==========================================
+ Hits         2744     2751       +7     
+ Misses        181      179       -2     

Files Changed	Coverage Δ
src/dask_awkward/lib/io/json.py	87.93% <ø> (ø)
src/dask_awkward/lib/io/parquet.py	92.39% <ø> (ø)
src/dask_awkward/lib/optimize.py	95.88% <90.90%> (+0.08%)	⬆️
src/dask_awkward/layers/layers.py	94.79% <100.00%> (+2.08%)	⬆️
src/dask_awkward/lib/inspect.py	93.54% <100.00%> (ø)

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[douglasdavis]

@agoose77 so far this is just the start of some code to be able to pass necessary_shape_columns around the dask-awkward code base inline with how we pass around necessary_columns. I think the major part of getting this to work will be in the __call__ methods; Once we've created an array with the necessary data columns, we can then (perhaps in unproject_layout, because we call unproject_layout in the __call__ methods, or in something preceeding/following unproject_layout) create PlaceholderArrays with known length for the columns that are necessary shape columns; we'll know which one's they are by tracking it as an attribute of the callable class, which is possible because AwkwardInputLayer.project_columns will get that information from the optimization pass

Does this sound reasonable?

[douglasdavis]

this None can be replaced by TypeTracerReport.shape_touched

[douglasdavis]

cc @lgray; if my comment above is the route we take then there will be some required changes in uproot (I'd be happy to help/do it- it should be simple- the function classes like upoot.dask.Uproot{OpenAnd}Read (if I'm remember the naming correctly) will need their project_columns implementations updated)

[lgray]

that shouldn't be a big issue!