how to update a field schema
The field will be named whatever you named it when you added it. If you can't remember, go to the "Manage fields" UI page for the relevant entity type/bundle and you'll be able to find it there.

The table names will be based on that field name; if the field is called field_my_field then the two database tables are:


field_data_field_my_field
field_revision_field_my_field