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ScyllaDB Python Driver is available under the Apache v2 License. ScyllaDB Python Driver is a fork of DataStax Python Driver. See Copyright here.
cassandra.cqlengine.models
- Table models for object mapping
cassandra.cqlengine.models
- Table models for object mapping¶The initializer creates an instance of the model. Pass in keyword arguments for columns you’ve defined on the model.
class Person(Model):
id = columns.UUID(primary_key=True)
first_name = columns.Text()
last_name = columns.Text()
person = Person(first_name='Blake', last_name='Eggleston')
person.first_name #returns 'Blake'
person.last_name #returns 'Eggleston'
Model attributes define how the model maps to tables in the database. These are class variables that should be set when defining Model deriviatives.
Optional. Indicates that this model is only intended to be used as a base class for other models. You can’t create tables for abstract models, but checks around schema validity are skipped during class construction.
Optional. Sets the name of the CQL table for this model. If left blank, the table name will be the name of the model, with it’s module name as it’s prefix. Manually defined table names are not inherited.
Optional. By default, __table_name__ is case insensitive. Set this to True if you want to preserve the case sensitivity.
Sets the name of the keyspace used by this model.
Sets the name of the default connection used by this model.
Will be deprecated in release 4.0. You can set the default ttl by configuring the table __options__
. See Default TTL and Per Query TTL for more details.
Optional Specifies a value for the discriminator column when using model inheritance.
See Model Inheritance for usage examples.
Each table can have its own set of configuration options, including compaction. Unspecified, these default to sensible values in
the server. To override defaults, set options using the model __options__
attribute, which allows options specified a dict.
When a table is synced, it will be altered to match the options set on your table. This means that if you are changing settings manually they will be changed back on resync.
Do not use the options settings of cqlengine if you want to manage your compaction settings manually.
See the list of supported table properties for more information.
For example:
class User(Model):
__options__ = {'compaction': {'class': 'LeveledCompactionStrategy',
'sstable_size_in_mb': '64',
'tombstone_threshold': '.2'},
'comment': 'User data stored here'}
user_id = columns.UUID(primary_key=True)
name = columns.Text()
or :
class TimeData(Model):
__options__ = {'compaction': {'class': 'SizeTieredCompactionStrategy',
'bucket_low': '.3',
'bucket_high': '2',
'min_threshold': '2',
'max_threshold': '64',
'tombstone_compaction_interval': '86400'},
'gc_grace_seconds': '0'}
Optional Setting False disables computing the routing key for TokenAwareRouting
The base methods allow creating, storing, and querying modeled objects.
Create an instance of this model in the database.
Takes the model column values as keyword arguments. Setting a value to None is equivalent to running a CQL DELETE on that column.
Returns the instance.
Check the existence of an object before insertion. The existence of an object is determined by its primary key(s). And please note using this flag would incur performance cost.
If the insertion isn’t applied, a LWTException
is raised.
try:
TestIfNotExistsModel.if_not_exists().create(id=id, count=9, text='111111111111')
except LWTException as e:
# handle failure case
print e.existing # dict containing LWT result fields
This method is supported on Cassandra 2.0 or later.
Check the existence of an object before an update or delete. The existence of an object is determined by its primary key(s). And please note using this flag would incur performance cost.
If the update or delete isn’t applied, a LWTException
is raised.
try:
TestIfExistsModel.objects(id=id).if_exists().update(count=9, text='111111111111')
except LWTException as e:
# handle failure case
pass
This method is supported on Cassandra 2.0 or later.
Saves an object to the database.
#create a person instance
person = Person(first_name='Kimberly', last_name='Eggleston')
#saves it to Cassandra
person.save()
Performs an update on the model instance. You can pass in values to set on the model for updating, or you can call without values to execute an update against any modified fields. If no fields on the model have been modified since loading, no query will be performed. Model validation is performed normally. Setting a value to None is equivalent to running a CQL DELETE on that column.
It is possible to do a blind update, that is, to update a field without having first selected the object out of the database. See Blind Updates
Checks to ensure that the values specified are correct on the Cassandra cluster. Simply specify the column(s) and the expected value(s). As with if_not_exists, this incurs a performance cost.
If the insertion isn’t applied, a LWTException
is raised.
t = TestTransactionModel(text='some text', count=5)
try:
t.iff(count=5).update('other text')
except LWTException as e:
# handle failure case
print e.existing # existing object
Returns a single object based on the passed filter constraints.
This is a pass-through to the model objects().:method:~cqlengine.queries.get.
Returns a queryset based on filter parameters.
This is a pass-through to the model objects().:method:~cqlengine.queries.filter.
Returns a queryset representing all stored objects
This is a pass-through to the model objects().all()
Deletes the object from the database
Sets the batch object to run instance updates and inserts queries with.
See Batch Queries for usage examples
Sets the timestamp for the query
Sets the ttl values to run instance updates and inserts queries with.
Change the context on the fly of the model instance (keyspace, connection)
Returns the column family name if it’s been defined otherwise, it creates it from the module and class name
Models also support dict-like access:
Returns the number of columns defined in the model
Returns the value of column col_name
Set m[col_name]
to value
Returns a list of column IDs.
Returns list of column values.
Returns a list of column ID/value tuples.
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ScyllaDB Python Driver is available under the Apache v2 License. ScyllaDB Python Driver is a fork of DataStax Python Driver. See Copyright here.
cassandra
- Exceptions and Enumscassandra.cluster
- Clusters and Sessionscassandra.policies
- Load balancing and Failure Handling Policiescassandra.auth
- Authenticationcassandra.graph
- Graph Statements, Options, and Row Factoriescassandra.metadata
- Schema and Ring Topologycassandra.metrics
- Performance Metricscassandra.query
- Prepared Statements, Batch Statements, Tracing, and Row Factoriescassandra.pool
- Hosts and Connection Poolscassandra.protocol
- Protocol Featurescassandra.encoder
- Encoders for non-prepared Statementscassandra.decoder
- Data Return Formatscassandra.concurrent
- Utilities for Concurrent Statement Executioncassandra.connection
- Low Level Connection Infocassandra.util
- Utilitiescassandra.timestamps
- Timestamp Generationcassandra.io.asyncioreactor
- asyncio
Event Loopcassandra.io.asyncorereactor
- asyncore
Event Loopcassandra.io.eventletreactor
- eventlet
-compatible Connectioncassandra.io.libevreactor
- libev
Event Loopcassandra.io.geventreactor
- gevent
-compatible Event Loopcassandra.io.twistedreactor
- Twisted Event Loopcassandra.cqlengine.models
- Table models for object mappingcassandra.cqlengine.columns
- Column types for object mapping modelscassandra.cqlengine.query
- Query and filter model objectscassandra.cqlengine.connection
- Connection management for cqlenginecassandra.cqlengine.management
- Schema management for cqlenginecassandra.cqlengine.usertype
- Model classes for User Defined Typescassandra.datastax.graph
- Graph Statements, Options, and Row Factoriescassandra.datastax.graph.fluent
cassandra.datastax.graph.fluent.query
cassandra.datastax.graph.fluent.predicates
On this page
cassandra.cqlengine.models
- Table models for object mappingModel
Model.__abstract__
Model.__table_name__
Model.__table_name_case_sensitive__
Model.__keyspace__
Model.__connection__
Model.__default_ttl__
Model.__discriminator_value__
Model.__options__
Model.__compute_routing_key__
Model.create()
Model.if_not_exists()
Model.if_exists()
Model.save()
Model.update()
Model.iff()
Model.get()
Model.filter()
Model.all()
Model.delete()
Model.batch()
Model.timeout()
Model.timestamp()
Model.ttl()
Model.using()
Model.column_family_name()
Model.len()
Model.m()
Model.keys()
Model.values()
Model.items()