fix(python,rust): Allow append/zip_with/extend on local categoricals

[c-peters]

fix #12091
fix #10393

[s-banach]

Sorry to bother you! Just wondering whether there's a path from here to joining on local categoricals.

[ritchie46]

I see that the finish always takes a materialized CategoricalChunked.

I think for now we must then update this return type. That means we don't have to return a "flattened" iterator, but can materialize via apply_generic which will ensure we traverse in the most optimal way.

But let's first get the bugs fixed and improve in a follow up PR.

[deanm0000]

Sorry to bother you! Just wondering whether there's a path from here to joining on local categoricals.

In the interim, pyarrow will join tables by categorical

pl.from_arrow(
df1.to_arrow().join(
df2.to_arrow(), keys='cat_col')
)

[c-peters]

Yes, in the future it would be possible to join on local categoricals with this merge operation.