Upgrade Guide¶

List Prepend Reversing¶

Legacy cqlengine included a workaround for a Cassandra bug in which prepended list segments were reversed (CASSANDRA-8733). As of this integration, this workaround is removed. The first released integrated version emits a warning when prepend is used. Subsequent versions will have this warning removed.

Date Column Type¶

The Date column type in legacy cqlengine used a timestamp CQL type and truncated the time. Going forward, the Date type represents a date for Cassandra 2.2+ (PYTHON-245). Users of the legacy functionality should convert models to use DateTime (which uses timestamp internally), and use the build-in datetime.date for input values.

Imports¶

cqlengine is now integrated as a sub-package of the driver base package ‘cassandra’. Upgrading will require adjusting imports to cqlengine. For example:

from cassandra.cqlengine import columns

is now:

from cassandra.cqlengine import columns

Package-Level Aliases¶

Legacy cqlengine defined a number of aliases at the package level, which became redundant when the package was integrated for a driver. These have been removed in favor of absolute imports, and referring to cannonical definitions. For example, cqlengine.ONE was an alias of cassandra.ConsistencyLevel.ONE. In the integrated package, only the cassandra.ConsistencyLevel remains.

Additionally, submodule aliases are removed from cqlengine in favor of absolute imports.

These aliases are removed, and not deprecated because they should be straightforward to iron out at module load time.

Exceptions¶

The legacy cqlengine.exceptions module had a number of Exception classes that were variously common to the package, or only used in specific modules. Common exceptions were relocated to cqlengine, and specialized exceptions were placed in the module that raises them. Below is a listing of updated locations:

UnicodeMixin Consolidation¶

class UnicodeMixin was defined in several cqlengine modules. This has been consolidated to a single definition in the cqlengine package init file. This is not technically part of the API, but noted here for completeness.

Float/Double Overload¶

Previously there was no Double column type. Doubles were modeled by specifying Float(double_precision=True). This inititializer parameter is now deprecated. Applications should use Double for CQL double, and Float for CQL float.

Schema Management¶

cassandra.cqlengine.management.create_keyspace is deprecated. Instead, use the new replication-strategy-specific functions that accept explicit options for known strategies:

• create_keyspace_simple()

• create_keyspace_network_topology()

cassandra.cqlengine.management.delete_keyspace is deprecated in favor of a new function, drop_keyspace(). The intent is simply to make the function match the CQL verb it invokes.

Model Inheritance¶

The names for class attributes controlling model inheritance are changing. Changes are as follows:

• Replace ‘polymorphic_key’ in the base class Column definition with discriminator_column

• Replace the ‘__polymorphic_key__’ class attribute the derived classes with __discriminator_value__

The functionality is unchanged – the intent here is to make the names and language around these attributes more precise. For now, the old names are just deprecated, and the mapper will emit warnings if they are used. The old names will be removed in a future version.

The example below shows a simple translation:

Before:

class Pet(Model):
    __table_name__ = 'pet'
    owner_id = UUID(primary_key=True)
    pet_id = UUID(primary_key=True)
    pet_type = Text(polymorphic_key=True)
    name = Text()

class Cat(Pet):
    __polymorphic_key__ = 'cat'

class Dog(Pet):
    __polymorphic_key__ = 'dog'

After:

class Pet(models.Model):
    __table_name__ = 'pet'
    owner_id = UUID(primary_key=True)
    pet_id = UUID(primary_key=True)
    pet_type = Text(discriminator_column=True)
    name = Text()

class Cat(Pet):
    __discriminator_value__ = 'cat'

class Dog(Pet):
    __discriminator_value__ = 'dog'

TimeUUID.from_datetime¶

This function is deprecated in favor of the core utility function uuid_from_time().