`from_arrow` is not zero-cost about polars HOT 2 CLOSED

Converting from Arrow is not always zero copy. We have a different string representation than what most existing Arrow implementations have. So the behavior here is expected.

from polars.

Hi, @stinodego,

I still have the following questions:

1. If it's like that, maybe the documentation should be explicit about that, no? I think string is a pretty common type and I think one would understand that the conversion is zero-cost.
2. In this example it's implied that the whole dataframe is copied. Because the memory required is double the dataframe size. If it's because of what you say, shouldn't it be only the string columns?
3. Is there anything we can do to circumvent this? Like using certain data type with pyarrow.
4. Will something similar happen with categories? Or is converting to categories first a good alternative if the number of different values of the string columns are small.

Thanks in advance,

from polars.