Migrated issue, originally created by Charles Leifer (@coleifer)

Hi, thanks for your excellent work on this project (and SQA).

I'm using Flask-migrate and ran into a small issue adding a column that had a foreign key constraint. The column was added, but the constraint was not created. I wasn't sure if this was operator error on my part, but thought I'd share it anyway:

I made some model changes in my project and noticed that a foreign key constraint wasn't getting picked up when I ran migrate. Basically I had a blog Entry model and added a User model to represent the author. I also added a foreign key from the entry to the user.

Here are portions of the models:

class Entry(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100))
    author_id = db.Column(db.Integer, db.ForeignKey('user.id'))  # New column
class User(db.Model):  # New model
    id = db.Column(db.Integer, primary_key=True)

This is the output of db migrate:

INFO  [alembic.migration] Context impl SQLiteImpl.
INFO  [alembic.migration] Will assume non-transactional DDL.
INFO  [alembic.autogenerate.compare] Detected added table 'user'
INFO  [alembic.autogenerate.compare] Detected added column 'entry.author_id'

Here is the migration:

    ### commands auto generated by Alembic - please adjust! ###
    op.create_table('user',
    sa.Column('id', sa.Integer(), nullable=False),
    ....
    sa.PrimaryKeyConstraint('id'),
    sa.UniqueConstraint('email'),
    sa.UniqueConstraint('slug')
    )
    op.add_column(u'entry', sa.Column('author_id', sa.Integer(), nullable=True))
    ### end Alembic commands ###

Notice that the foreign key constraint is missing.

I upgraded the db and, while the author_id column is there, the foreign key constraint is not:

CREATE TABLE entry (
	id INTEGER NOT NULL,
	title VARCHAR(100),
        author_id INTEGER,
	PRIMARY KEY (id),
	UNIQUE (slug)
);

Versions:

Flask-Migrate==1.2.0
Flask-SQLAlchemy==1.0
SQLAlchemy==0.9.1
alembic==0.6.2