Substrait + identifier normalization flags issues

[alamb]

Describe the bug

This is a report from @lmwnshn and is part of

• [DISCUSSION] Lowering the barrier to new users (Lessons from-799 CMU Optimizer Class) #14373

enable_ident_normalization: I think there may be some extra complications in my situation arising from the use of Substrait (or perhaps Substrait table names are treated as quoted?

In particular, with enable_ident_normalization=false, I cannot register lowercase tablenames and lowercase column names in the parquet files as shown here:

To Reproduce

Please see
https://github.com/lmwnshn/15799-s25-project1-remnants/blob/main/run_datafusion_ident.py#L37

In particular, with enable_ident_normalization=false, I cannot register lowercase tablenames and lowercase column names in the parquet files as shown here:
https://github.com/lmwnshn/15799-s25-project1-remnants/blob/main/run_datafusion_ident.py#L12-L19

So I had to hack the parquet files up a bit
https://github.com/lmwnshn/15799-s25-project1-remnants/blob/main/fix_parquet.py#L11-L23

and switch to uppercased column names + register tables as uppercase
https://github.com/lmwnshn/15799-s25-project1-remnants/blob/main/run_datafusion.py#L12-L19
to get the Substrait plan to execute successfully.

Expected behavior

I expect that the I can register lowercase tablenames and lowercase column names in the parquet files

Additional context

No response