How to paginate a secondary table using SQLALCHEMY in Flask? - flask

Question

I am trying to paginate a secondary table for Client but it doesn't work, the results always more than the per_page parameter that by default shows only three items per page .
Here is my models.py:
subscribers = db.Table(
'clients_subscribed',
db.Column('client_id', db.Integer, db.ForeignKey('client.id', ondelete='CASCADE')),
db.Column('user_id', db.Integer, db.ForeignKey('user.id', ondelete='CASCADE'))
)
class Client(db.Model, UserMixin):
id = db.Column(db.Integer(), primary_key=True)
public_id = db.Column(db.String(50), default=uuid.uuid4)
name = db.Column(db.String())
subscribed_users = db.relationship(
'User',
secondary=subscribers,
backref=db.backref('user', passive_deletes=True, lazy='dynamic')
)
Here is also my views.py :
from flask import current_app
current_app.config['SUBSCRIBERS_PER_PAGE'] = 3
#api_route.route('/client/subscribers/<string:category>/<string:client_id>', methods=['GET'])
#token_required
def subscribers(current_user, category, client_id):
if request.method == 'GET':
page = request.args.get('page', 1, type=int)
client = Client.query.filter_by(public_id=client_id).first()
if not client:
raise InvalidUsage(u'404, not found!', status_code=404)
pagination = # Paginate Client.subscribed_users
psubscribers = pagination.items
subscribers = {}
prev = None
if pagination.has_prev:
prev = url_for('api.subscribers', category=category, client_id=client_id, page=page-1, _external=True)
next = None
if pagination.has_next:
next = url_for('api.subscribers', category=category, client_id=client_id, page=page+1, _external=True)
for client in client.subscribed_users:
subscribers_case = {
'id': client.id,
'public_id': client.public_id,
'image': '/static/img/'+client.image if client.image else '/static/img/logo.png',
'name': client.name,
}
subscribers[client.public_id] = subscribers_case
return jsonify({
'subscribers' : subscribers,
'prev' : prev,
'next': next,
'count' : pagination.total
})
return jsonify({'error' : 'No data!'})
Also here is the class User in models:
class User(db.Model, UserMixin):
__tablename__ = 'user'
id = db.Column(db.Integer(), primary_key=True)
public_id = db.Column(db.String(50), default=uuid.uuid4)
name = db.Column(db.String())
family = db.Column(db.String())
bio = db.Column(db.String())
tele = db.Column(db.String(), unique=True)
password = db.Column(db.String())
clients = db.relationship('Client', backref='user', passive_deletes=True, lazy='dynamic')
news = db.relationship('News', backref='user', passive_deletes=True, lazy='dynamic')
notifications = db.relationship('Notification', backref='user', passive_deletes=True, lazy='dynamic')
image = db.Column(db.String(), nullable=True)
slug = db.Column(db.String())
roles = db.relationship(
'Role',
secondary=roles,
backref=db.backref('users', lazy='joined',
passive_deletes=True,
single_parent=True)
)
subscribed_clients = db.relationship(
'Client',
secondary=subscribers,
backref=db.backref('client', passive_deletes=True, lazy='joined')
)
Any suggestions guys how to make that work !!!

Answer 1

You need to use lazy=dynamic in the relationship in order to get a Query object back. Documentation here, and another StackOverflow question about this here.