IntegrityError when inserting model with composite primary key

Question

I am trying to create a table with composite primary keys. It has one integer and two string fields as the key. When I commit the session it raises an IntegrityError . What is wrong with what I am doing?

class Targets(db.Model):
    __tablename__ = 'Targets'
    id = db.Column(db.Integer, primary_key=True)
    Event_Name = db.Column(db.String, index=True, default='Single_Trigger', primary_key=True)
    Trigger_id = db.Column(db.String, index=True, unique=True, primary_key=True)

>>> from app import db, models
>>> target = models.Targets(Trigger_id='20150421_221942_ST_1')
>>> db.session.add(target)
>>> db.session.commit()

IntegrityError: (IntegrityError) NOT NULL constraint failed: Targets.id u'INSERT INTO "Targets" ("Event_Name", "Name", "Trigger_id", "Tile", "Status", "RA", "Dec", "Filter", "Exp_time", "No_Exp") VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)' ('Single_Trigger', '20150421_221942_ST_1', '20150421_221942_ST_1', 1, 0, 102.0, 231.25, 'V', 30, 5)

Answer 1

SQLAlchemy doesn't set auto-increment on composite keys, you need to set autoincrement=True on the id column.

http://docs.sqlalchemy.org/en/latest/core/metadata.html#sqlalchemy.schema.Column.params.autoincrement

If the table has a composite primary key consisting of more than one integer column, set this flag to True only on the column that should be considered “autoincrement”.

Answer 2

Yo have to set autoincrement=True , explicit in the primary key:

class Targets(db.Model):
    __tablename__ = 'Targets'
    id = db.Column(db.Integer, primary_key=True)
    Event_Name = db.Column(db.String, index=True, default='Single_Trigger', primary_key=True)
    Trigger_id = db.Column(db.String, index=True, unique=True, primary_key=True)

The important part is that you have to downgrade to the previous migration, delete the migration and create new one and upgrate to it.