example_mapper.py

#!/usr/bin/env python

# Copyright 2013-2016 DataStax, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# silence warnings just for demo -- applications would typically not do this
import os
os.environ['CQLENG_ALLOW_SCHEMA_MANAGEMENT'] = '1'

import logging

log = logging.getLogger()
log.setLevel('INFO')
handler = logging.StreamHandler()
handler.setFormatter(logging.Formatter("%(asctime)s [%(levelname)s] %(name)s: %(message)s"))
log.addHandler(handler)

from uuid import uuid4

from cassandra.cqlengine import columns
from cassandra.cqlengine import connection
from cassandra.cqlengine import management
from cassandra.cqlengine import ValidationError
from cassandra.cqlengine.models import Model
from cassandra.cqlengine.query import BatchQuery, LWTException

KEYSPACE = "testkeyspace"


class FamilyMembers(Model):
 __keyspace__ = KEYSPACE
 id = columns.UUID(primary_key=True, default=uuid4)
 surname = columns.Text(primary_key=True)
 name = columns.Text(primary_key=True)
 birth_year = columns.Integer()
 sex = columns.Text(min_length=1, max_length=1)

 def validate(self):
 super(FamilyMembers, self).validate()
 if self.sex and self.sex not in 'mf':
 raise ValidationError("FamilyMember.sex must be one of ['m', 'f']")

 if self.birth_year and self.sex == 'f':
 raise ValidationError("FamilyMember.birth_year is set, and 'a lady never tells'")


def main():
 connection.default()

 # Management functions would normally be used in development, and possibly for deployments.
 # They are typically not part of a core application.
 log.info("### creating keyspace...")
 management.create_keyspace_simple(KEYSPACE, 1)
 log.info("### syncing model...")
 management.sync_table(FamilyMembers)

 # default uuid is assigned
 simmons = FamilyMembers.create(surname='Simmons', name='Gene', birth_year=1949, sex='m')

 # add members to his family later
 FamilyMembers.create(id=simmons.id, surname='Simmons', name='Nick', birth_year=1989, sex='m')
 sophie = FamilyMembers.create(id=simmons.id, surname='Simmons', name='Sophie', sex='f')

 nick = FamilyMembers.objects(id=simmons.id, surname='Simmons', name='Nick')
 try:
 nick.iff(birth_year=1988).update(birth_year=1989)
 except LWTException:
 print "precondition not met"

 log.info("### setting individual column to NULL by updating it to None")
 nick.update(birth_year=None)

 # showing validation
 try:
 FamilyMembers.create(id=simmons.id, surname='Tweed', name='Shannon', birth_year=1957, sex='f')
 except ValidationError:
 log.exception('INTENTIONAL VALIDATION EXCEPTION; Failed creating instance:')
 FamilyMembers.create(id=simmons.id, surname='Tweed', name='Shannon', sex='f')

 log.info("### add multiple as part of a batch")
 # If creating many at one time, can use a batch to minimize round-trips
 hogan_id = uuid4()
 with BatchQuery() as b:
 FamilyMembers.batch(b).create(id=hogan_id, surname='Hogan', name='Hulk', sex='m')
 FamilyMembers.batch(b).create(id=hogan_id, surname='Hogan', name='Linda', sex='f')
 FamilyMembers.batch(b).create(id=hogan_id, surname='Hogan', name='Nick', sex='m')
 FamilyMembers.batch(b).create(id=hogan_id, surname='Hogan', name='Brooke', sex='f')

 log.info("### All members")
 for m in FamilyMembers.all():
 print m, m.birth_year, m.sex

 log.info("### Select by partition key")
 for m in FamilyMembers.objects(id=simmons.id):
 print m, m.birth_year, m.sex

 log.info("### Constrain on clustering key")
 for m in FamilyMembers.objects(id=simmons.id, surname=simmons.surname):
 print m, m.birth_year, m.sex

 log.info("### Constrain on clustering key")
 kids = FamilyMembers.objects(id=simmons.id, surname=simmons.surname, name__in=['Nick', 'Sophie'])

 log.info("### Delete a record")
 FamilyMembers(id=hogan_id, surname='Hogan', name='Linda').delete()
 for m in FamilyMembers.objects(id=hogan_id):
 print m, m.birth_year, m.sex

 management.drop_keyspace(KEYSPACE)

if __name__ == "__main__":
 main()