Redefine Multiselect Field after migration

[dlenskyi]

Hi there! Earlier I used PositiveSmallIntegerField with choices option, so user could choose only one variant among my choices.
Now, I needed to implement multiple choices with that field, so I used this library for doing this.
Everything is working fine, but when I altered my field with MultipleChoiceField, my older records in database with old PositiveSmallIntegerField became empty, I think because nativery MultiSelectField stores values in type of CharField, but PositiveSmallIntegerField stores them as integers. How can I fix that problem and reassign older records in DB for that field to new values (e.g. choices of new MultiSelectField)