The final topic we will discuss in this chapter is how to make modifications to an existing Model definition. From the project specification, we know we would like to be able to save drafts of our blog entries. Right now we don't have any way to tell whether an entry is a draft or not, so we will need to add a column that lets us store the status of our entry. Unfortunately, while
db.create_all() works perfectly for creating tables, it will not automatically modify an existing table; to do this we need to use migrations.
We will use Flask-Migrate to help us automatically update our database whenever we change the schema. In the blog virtualenv, install Flask-Migrate using