Flask-CQLAlchemy

Flask-CQLAlchemy handles connections to Cassandra clusters and gives a unified easier way to declare models and their columns

Now with support for abstract models and UserDefinedTypes

Installation

pip install flask-cqlalchemy

Dependencies

As such Flask-CQLAlchemy depends only on the cassandra-driver. It is assumed that you already have flask installed.

Flask-CQLAlchemy has been tested with versions 2.6.0, 2.7.2, 3.0.0 and 3.1.0 of cassandra-driver. It is known to work with all versions >=2.5, but use it at your own risk. All previous versions of Flask-CQLAlchemy are deprecated.

Example

#example_app.py
import uuid
from flask import Flask
from flask.ext.cqlalchemy import CQLAlchemy

app = Flask(__name__)
app.config['CASSANDRA_HOSTS'] = ['127.0.0.1']
app.config['CASSANDRA_KEYSPACE'] = "cqlengine"
db = CQLAlchemy(app)


class User(db.Model):
    uid = db.columns.UUID(primary_key=True, default=uuid.uuid4)
    username = db.columns.Text(required=False)

User Defined Types

#example_app_udt.py
import uuid
from flask import Flask
from flask_cqlalchemy import CQLAlchemy

app = Flask(__name__)
app.config['CASSANDRA_HOSTS'] = ['127.0.0.1']
app.config['CASSANDRA_KEYSPACE'] = "cqlengine"
app.config['CASSANDRA_SETUP_KWARGS'] = {'protocol_version': 3}
db = CQLAlchemy(app)


class address(db.UserType):
    street = db.columns.Text()
    zipcode = db.columns.Integer()

class users(db.Model):
    __keyspace__ = 'cqlengine'
    name = db.columns.Text(primary_key=True)
    addr = db.columns.UserDefinedType(address)

Usage

Start a python shell

>>>from example_app import db, User
>>>db.sync_db()
>>>user1 = User.create(username='John Doe')

User Defined Types

>>>from example_app_udt import db, address, users
>>>db.sync_db()
>>>user_address = address(street="Easy St.", zipcode=99999
>>> user
users(name=u'Joe', addr=<example_app_udt.address object at 0x7f4498063310>)
>>> user.addr
<example_app_udt.address object at 0x7f4498063310>
>>> user.addr.street
u'Easy St.'
>>> user.addr.zipcode
99999

For a complete list of available methods refer to the cqlengine Model documentation

Configuration Options

CQLAlchemy provides all the option available in the cqlengine connection.setup() method

• CASSANDRA_HOSTS - A list of hosts
• CASSANDRA_KEYSPACE - The default keyspace to use
• CASSANDRA_CONSISTENCY - The global default ConsistencyLevel
• CASSANDRA_LAZY_CONNECT - True if should not connect until first use
• CASSANDRA_RETRY_CONNECT - True if we should retry to connect even if there was a connection failure initially
• CASSANDRA_SETUP_KWARGS - Pass-through keyword arguments for Cluster()

Beta Features

Flask CQLAlchemy supports User Defined Types, provided you are using Cassandra versions 2.1 or above. However Travis only provides 2.0.9 for testing and so this feature has not undergone rigorous testing.

Contributing

Found a bug? Need a feature? Open it in issues, or even better, open a PR. Please include tests in the PR.