The Python driver for Cassandra offers several methods for executing queries.
You can synchronously block for queries to complete using
Session.execute(), you can obtain asynchronous request futures through
Session.execute_async(), and you can attach a callback to the future
Examples of multiple request patterns can be found in the benchmark scripts included in the driver project.
The choice of execution pattern will depend on the application context. For applications dealing with multiple
requests in a given context, the recommended pattern is to use concurrent asynchronous
requests with callbacks. For many use cases, you don’t need to implement this pattern yourself.
provide this pattern with a synchronous API and tunable concurrency.
Due to the GIL and limited concurrency, the driver can become CPU-bound pretty quickly. The sections below discuss further runtime and design considerations for mitigating this limitation.
PyPy is an alternative Python runtime which uses a JIT compiler to reduce CPU consumption. This leads to a huge improvement in the driver performance, more than doubling throughput for many workloads.
Cython is an optimizing compiler and language that can be used to compile the core files and optional extensions for the driver. Cython is not a strict dependency, but the extensions will be built by default.
See Installation for details on controlling this build.
All of the patterns discussed above may be used over multiple processes using the multiprocessing module. Multiple processes will scale better than multiple threads, so if high throughput is your goal, consider this option.
For further discussion and simple examples using the driver with
see this blog post.
cassandra- Exceptions and Enums
cassandra.cluster- Clusters and Sessions
cassandra.policies- Load balancing and Failure Handling Policies
cassandra.graph- Graph Statements, Options, and Row Factories
cassandra.metadata- Schema and Ring Topology
cassandra.metrics- Performance Metrics
cassandra.query- Prepared Statements, Batch Statements, Tracing, and Row Factories
cassandra.pool- Hosts and Connection Pools
cassandra.protocol- Protocol Features
cassandra.encoder- Encoders for non-prepared Statements
cassandra.decoder- Data Return Formats
cassandra.concurrent- Utilities for Concurrent Statement Execution
cassandra.connection- Low Level Connection Info
cassandra.timestamps- Timestamp Generation
gevent-compatible Event Loop
cassandra.io.twistedreactor- Twisted Event Loop
cassandra.cqlengine.models- Table models for object mapping
cassandra.cqlengine.columns- Column types for object mapping models
cassandra.cqlengine.query- Query and filter model objects
cassandra.cqlengine.connection- Connection management for cqlengine
cassandra.cqlengine.management- Schema management for cqlengine
cassandra.cqlengine.usertype- Model classes for User Defined Types
cassandra.datastax.graph- Graph Statements, Options, and Row Factories