Hi ! Computing the fingerprint of the mapped dataset is necessary for the caching mechanism to work.
So you can disable this with set_caching_enabled(True), but every time you re-run your code it will recompute the map call.
The fingerprint is computed by hashing the code and the variables in your map function. So it takes time because it hashes your big dictionary. It could be helpful if you could specify the hash of your dictionary in advance maybe. Or if you could specify in advance the fingerprint of the resulting dataset. What do you think ?