Polars treats strings as large_strings automatically

[Schwarzam]

The code below is trying to apply the conversion before writing to the buffer to respond. It does not apply any dtype change to the column.
I tryed multiple ways but the lack of documentation and access to low level in polars limits this possibility of conversion.

use polars::prelude::*;
// Converting from LargeUtf8 to Utf8
let col_names = df.get_column_names_owned();
for (index, name) in col_names.iter().enumerate() {
    
    let col = df.column(&name).unwrap();
    if col.dtype() == &ArrowDataType::LargeUtf8 {
        let new_col = &col.strict_cast(&DataType::from_arrow(&ArrowDataType::Utf8, true))?;
        //let new_col = col.u8().unwrap();
        df.replace_column(index, new_col.to_owned().into_series()).unwrap();
    }
}

// Checking if anything changed
for (index, name) in col_names.iter().enumerate() {
    let col = df.column(&name).unwrap();
    if col.dtype() == &ArrowDataType::LargeUtf8 {
        println!("Column in LargeUtf8 {:?}", name);
    }
}

[Schwarzam]

Fixed on #3