# Upgrading

## Upgrading from dse-driver

Since 3.21.0, cassandra-driver fully supports DataStax products. dse-driver and dse-graph users should now migrate to cassandra-driver to benefit from latest bug fixes and new features. The upgrade to this new unified driver version is straightforward with no major API changes.

### Installation

Only the cassandra-driver package should be installed. dse-driver and dse-graph are not required anymore:

    pip install cassandra-driver

If you need the Graph Fluent API (features provided by dse-graph):

    pip install cassandra-driver[graph]

See Installation for more details.

### Import from the cassandra module

There is no dse module, so you should import from the cassandra module. You need to change only the first module of your import statements, not the submodules.

    from dse.cluster import Cluster, EXEC_PROFILE_GRAPH_DEFAULT
    from dse.auth import PlainTextAuthProvider
    from dse.policies import WhiteListRoundRobinPolicy

    # becomes

    from cassandra.cluster import Cluster, EXEC_PROFILE_GRAPH_DEFAULT
    from cassandra.auth import PlainTextAuthProvider
    from cassandra.policies import WhiteListRoundRobinPolicy

Also note that the cassandra.hosts module doesn’t exist in cassandra-driver. This module is named cassandra.pool.

### dse-graph

dse-graph features are now built-in in cassandra-driver. The only change you need to do is your import statements:

    from dse_graph import ..
    from dse_graph.query import ..

    # becomes

    from cassandra.datastax.graph.fluent import ..
    from cassandra.datastax.graph.fluent.query import ..

See `fluent`.

### Session.execute and Session.execute_async API

Although it is not common to use this API with positional arguments, it is important to be aware that the host and execute_as parameters have had their positional order swapped. This is only because execute_as was added in dse-driver before host.

See `Session.execute()`.

### Deprecations

These changes are optional, but recommended:

- Importing from cassandra.graph is deprecated. Consider importing from cassandra.datastax.graph.

- Use `DefaultLoadBalancingPolicy` instead of DSELoadBalancingPolicy.

## Upgrading to 3.0

Version 3.0 of the DataStax Python driver for Apache Cassandra adds support for Cassandra 3.0 while maintaining support for previously supported versions. In addition to substantial internal rework, there are several updates to the API that integrators will need to consider:

### Default consistency is now `LOCAL_ONE`

Previous value was `ONE`. The new value is introduced to mesh with the default DC-aware load balancing policy and to match other drivers.

### Execution API Updates

#### Result return normalization

PYTHON-368

Previously results would be returned as a `list` of rows for result rows up to `fetch_size`, and `PagedResult` afterward. This could break application code that assumed one type and got another.

Now, all results are returned as an iterable `ResultSet`.

The preferred way to consume results of unknown size is to iterate through them, letting automatic paging occur as they are consumed.

    results = session.execute("SELECT * FROM system.local")
    for row in results:
        process(row)

If the expected size of the results is known, it is still possible to materialize a list using the iterator:

    results = session.execute("SELECT * FROM system.local")
    row_list = list(results)

For backward compatibility, `ResultSet` supports indexing. When accessed at an index, a ~.ResultSet object will materialize all its pages:

    results = session.execute("SELECT * FROM system.local")
    first_result = results[0]  # materializes results, fetching all pages

This can send requests and load (possibly large) results into memory, so ~.ResultSet will log a warning on implicit materialization.

#### Trace information is not attached to executed Statements

PYTHON-318

Previously trace data was attached to Statements if tracing was enabled. This could lead to confusion if the same statement was used for multiple executions.

Now, trace data is associated with the `ResponseFuture` and `ResultSet` returned for each query:

`ResponseFuture.get_query_trace()`

`ResponseFuture.get_all_query_traces()`

`ResultSet.get_query_trace()`

`ResultSet.get_all_query_traces()`

#### Binding named parameters now ignores extra names

PYTHON-178

Previously, `BoundStatement.bind()` would raise if a mapping was passed with extra names not found in the prepared statement.

Behavior in 3.0+ is to ignore extra names.

### blist removed as soft dependency

PYTHON-385

Previously the driver had a soft dependency on `blist sortedset`, using that where available and using an internal fallback where possible.

Now, the driver never chooses the `blist` variant, instead returning the internal `util.SortedSet` for all `set` results. The class implements all standard set operations, so no integration code should need to change unless it explicitly checks for `sortedset` type.

### Metadata API Updates

PYTHON-276, PYTHON-408, PYTHON-400, PYTHON-422

Cassandra 3.0 brought a substantial overhaul to the internal schema metadata representation. This version of the driver supports that metadata in addition to the legacy version. Doing so also brought some changes to the metadata model.

The present API is documented: `cassandra.metadata`. Changes highlighted below:

- All types are now exposed as CQL types instead of types derived from the internal server implementation

- Some metadata attributes have changed names to match current nomenclature (for example, `Index.kind` in place of `Index.type`).

- Some metadata attributes removed

  - `TableMetadata.keyspace` reference replaced with `TableMetadata.keyspace_name`

  - `ColumnMetadata.index` is removed table- and keyspace-level mappings are still maintained

### Several deprecated features are removed

PYTHON-292

- `ResponseFuture.result` timeout parameter is removed, use `Session.execute` timeout instead (031ebb0)

- `Cluster.refresh_schema` removed, use `Cluster.refresh_*_metadata` instead (419fcdf)

- `Cluster.submit_schema_refresh` removed (574266d)

- `cqltypes` time/date functions removed, use `util` entry points instead (bb984ee)

- `decoder` module removed (e16a073)

- `TableMetadata.keyspace` attribute replaced with `keyspace_name` (cc94073)

- `cqlengine.columns.TimeUUID.from_datetime` removed, use `util` variant instead (96489cc)

- `cqlengine.columns.Float(double_precision)` parameter removed, use `columns.Double` instead (a2d3a98)

- `cqlengine` keyspace management functions are removed in favor of the strategy-specific entry points (4bd5909)

- `cqlengine.Model.__polymorphic_*__` attributes removed, use `__discriminator*` attributes instead (9d98c8e)

- `cqlengine.statements` will no longer warn about list list prepend behavior (79efe97)

## Upgrading to 2.1 from 2.0

Version 2.1 of the DataStax Python driver for Apache Cassandra adds support for Cassandra 2.1 and version 3 of the native protocol.

Cassandra 1.2, 2.0, and 2.1 are all supported. However, 1.2 only supports protocol version 1, and 2.0 only supports versions 1 and 2, so some features may not be available.

### Using the v3 Native Protocol

By default, the driver will attempt to use version 2 of the native protocol. To use version 3, you must explicitly set the `protocol_version`:

    from cassandra.cluster import Cluster

    cluster = Cluster(protocol_version=3)

Note that protocol version 3 is only supported by Cassandra 2.1+.

In future releases, the driver may default to using protocol version 3.

### Working with User-Defined Types

Cassandra 2.1 introduced the ability to define new types:

    USE KEYSPACE mykeyspace;

    CREATE TYPE address (street text, city text, zip int);

The driver generally expects you to use instances of a specific class to represent column values of this type. You can let the driver know what class to use with `Cluster.register_user_type()`:

    cluster = Cluster()

    class Address(object):

        def __init__(self, street, city, zipcode):
            self.street = street
            self.city = text
            self.zipcode = zipcode

    cluster.register_user_type('mykeyspace', 'address', Address)

When inserting data for `address` columns, you should pass in instances of `Address`. When querying data, `address` column values will be instances of `Address`.

If no class is registered for a user-defined type, query results will use a `namedtuple` class and data may only be inserted though prepared statements.

See User Defined Types for more details.

### Customizing Encoders for Non-prepared Statements

Starting with version 2.1 of the driver, it is possible to customize how Python types are converted to CQL literals when working with non-prepared statements. This is done on a per-`Session` basis through `Session.encoder`:

    cluster = Cluster()
    session = cluster.connect()
    session.encoder.mapping[tuple] = session.encoder.cql_encode_tuple

See Type Conversions for the table of default CQL literal conversions.

### Using Client-Side Protocol-Level Timestamps

With version 3 of the native protocol, timestamps may be supplied by the client at the protocol level. (Normally, if they are not specified within the CQL query itself, a timestamp is generated server-side.)

When `protocol_version` is set to 3 or higher, the driver will automatically use client-side timestamps with microsecond precision unless `Session.use_client_timestamp` is changed to `False`. If a timestamp is specified within the CQL query, it will override the timestamp generated by the driver.

## Upgrading to 2.0 from 1.x

Version 2.0 of the DataStax Python driver for Apache Cassandra includes some notable improvements over version 1.x. This version of the driver supports Cassandra 1.2, 2.0, and 2.1. However, not all features may be used with Cassandra 1.2, and some new features in 2.1 are not yet supported.

### Using the v2 Native Protocol

By default, the driver will attempt to use version 2 of Cassandra’s native protocol. You can explicitly set the protocol version to 2, though:

    from cassandra.cluster import Cluster

    cluster = Cluster(protocol_version=2)

When working with Cassandra 1.2, you will need to explicitly set the `protocol_version` to 1:

    from cassandra.cluster import Cluster

    cluster = Cluster(protocol_version=1)

### Automatic Query Paging

Version 2 of the native protocol adds support for automatic query paging, which can make dealing with large result sets much simpler.

See Paging Large Queries for full details.

### Protocol-Level Batch Statements

With version 1 of the native protocol, batching of statements required using a BATCH cql query. With version 2 of the native protocol, you can now batch statements at the protocol level. This allows you to use many different prepared statements within a single batch.

See `BatchStatement` for details and usage examples.

### SASL-based Authentication

Also new in version 2 of the native protocol is SASL-based authentication. See the section on Security for details and examples.

### Lightweight Transactions

Lightweight transactions are another new feature. To use lightweight transactions, add `IF` clauses to your CQL queries and set the `serial_consistency_level` on your statements.

### Calling Cluster.shutdown()

In order to fix some issues around garbage collection and unclean interpreter shutdowns, version 2.0 of the driver requires you to call `Cluster.shutdown()` on your `Cluster` objects when you are through with them. This helps to guarantee a clean shutdown.

### Deprecations

The following functions have moved from `cassandra.decoder` to `cassandra.query`. The original functions have been left in place with a `DeprecationWarning` for now:

- `cassandra.decoder.tuple_factory` has moved to `cassandra.query.tuple_factory`

- `cassandra.decoder.named_tuple_factory` has moved to `cassandra.query.named_tuple_factory`

- `cassandra.decoder.dict_factory` has moved to `cassandra.query.dict_factory`

- `cassandra.decoder.ordered_dict_factory` has moved to `cassandra.query.ordered_dict_factory`

### Dependency Changes

The following dependencies have officially been made optional:

- `scales`

- `blist`

And one new dependency has been added (to enable Python 3 support):

- `six`