deb-python-cassandra-driver/docs/object_mapper.rst

Object Mapper

cqlengine is the Cassandra CQL 3 Object Mapper packaged with this driver

Jump to Getting Started <getting-started>

Contents

cqlengine/upgrade_guide

For migrating projects from legacy cqlengine, to the integrated product

cqlengine/models

Examples defining models, and mapping them to tables

cqlengine/queryset

Overview of query sets and filtering

cqlengine/batches

Working with batch mutations

API Documentation <om_api>

Index of API documentation

cqlengine/third_party

High-level examples in Celery and uWSGI

cqlengine/faq

cqlengine/upgrade_guide cqlengine/models cqlengine/queryset cqlengine/batches cqlengine/third_party cqlengine/faq

Getting Started

import uuid
from cassandra.cqlengine import columns
from cassandra.cqlengine import connection
from datetime import datetime
from cassandra.cqlengine.management import sync_table
from cassandra.cqlengine.models import Model

#first, define a model
class ExampleModel(Model):
    example_id      = columns.UUID(primary_key=True, default=uuid.uuid4)
    example_type    = columns.Integer(index=True)
    created_at      = columns.DateTime()
    description     = columns.Text(required=False)

#next, setup the connection to your cassandra server(s)...
# see http://datastax.github.io/python-driver/api/cassandra/cluster.html for options
# the list of hosts will be passed to create a Cluster() instance
connection.setup(['127.0.0.1'], "cqlengine", protocol_version=3)

#...and create your CQL table
>>> sync_table(ExampleModel)

#now we can create some rows:
>>> em1 = ExampleModel.create(example_type=0, description="example1", created_at=datetime.now())
>>> em2 = ExampleModel.create(example_type=0, description="example2", created_at=datetime.now())
>>> em3 = ExampleModel.create(example_type=0, description="example3", created_at=datetime.now())
>>> em4 = ExampleModel.create(example_type=0, description="example4", created_at=datetime.now())
>>> em5 = ExampleModel.create(example_type=1, description="example5", created_at=datetime.now())
>>> em6 = ExampleModel.create(example_type=1, description="example6", created_at=datetime.now())
>>> em7 = ExampleModel.create(example_type=1, description="example7", created_at=datetime.now())
>>> em8 = ExampleModel.create(example_type=1, description="example8", created_at=datetime.now())

#and now we can run some queries against our table
>>> ExampleModel.objects.count()
8
>>> q = ExampleModel.objects(example_type=1)
>>> q.count()
4
>>> for instance in q:
>>>     print instance.description
example5
example6
example7
example8

#here we are applying additional filtering to an existing query
#query objects are immutable, so calling filter returns a new
#query object
>>> q2 = q.filter(example_id=em5.example_id)

>>> q2.count()
1
>>> for instance in q2:
>>>     print instance.description
example5