Great question! Dask dataframe does not support the dataframe data model, similar to Spark Dataframes. There are several dataframe functionalities that Dask fundementally cannot support because of Dask dataframe’s architecture and the data model deviations they made in its design. This gets at the core of this post: Not everything that is marketed as a dataframe is a dataframe. In the preprint we have a bit more about Dask and the deviations it has made.

From an implementation standpoint, I have made a post about this on the Modin GitHub: https://github.com/modin-project/modin/issues/515.