Apache Cassandra
-----------------

Apache Cassandra is a highly-scalable partitioned row store. Rows are organized into tables with a required primary key.

https://cwiki.apache.org/confluence/display/CASSANDRA2/Partitioners[Partitioning] means that Cassandra can distribute your data across multiple machines in an application-transparent matter. Cassandra will automatically repartition as machines are added and removed from the cluster.

https://cwiki.apache.org/confluence/display/CASSANDRA2/DataModel[Row store] means that like relational databases, Cassandra organizes data by rows and columns. The Cassandra Query Language (CQL) is a close relative of SQL.

For more information, see https://cassandra.apache.org/[the Apache Cassandra web site].

Issues should be reported on https://issues.apache.org/jira/projects/CASSANDRA/issues/[The Cassandra Jira].

Requirements
------------
- Java: see supported versions in build.xml (search for property "java.supported").
- Python: for `cqlsh`, see `bin/cqlsh` (search for function "is_supported_version").


Getting started
---------------

This short guide will walk you through getting a basic one node cluster up
and running, and demonstrate some simple reads and writes. For a more-complete guide, please see the Apache Cassandra website's https://cassandra.apache.org/doc/5.0/cassandra/getting-started/index.html[Getting Started Guide].

First, we'll unpack our archive:

  $ tar -zxvf apache-cassandra-$VERSION.tar.gz
  $ cd apache-cassandra-$VERSION

After that we start the server. Running the startup script with the -f argument will cause
Cassandra to remain in the foreground and log to standard out; it can be stopped with ctrl-C.

  $ bin/cassandra -f

Now let's try to read and write some data using the Cassandra Query Language:

  $ bin/cqlsh

The command line client is interactive so if everything worked you should
be sitting in front of a prompt:

----
Connected to Test Cluster at localhost:9160.
[cqlsh 6.2.0 | Cassandra 5.0-SNAPSHOT | CQL spec 3.4.7 | Native protocol v5]
Use HELP for help.
cqlsh>
----

As the banner says, you can use 'help;' or '?' to see what CQL has to
offer, and 'quit;' or 'exit;' when you've had enough fun. But lets try
something slightly more interesting:

----
cqlsh> CREATE KEYSPACE schema1
       WITH replication = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
cqlsh> USE schema1;
cqlsh:Schema1> CREATE TABLE users (
                 user_id varchar PRIMARY KEY,
                 first varchar,
                 last varchar,
                 age int
               );
cqlsh:Schema1> INSERT INTO users (user_id, first, last, age)
               VALUES ('jsmith', 'John', 'Smith', 42);
cqlsh:Schema1> SELECT * FROM users;
 user_id | age | first | last
---------+-----+-------+-------
  jsmith |  42 |  john | smith
cqlsh:Schema1>
----

If your session looks similar to what's above, congrats, your single node
cluster is operational!

For more on what commands are supported by CQL, see
https://cassandra.apache.org/doc/5.0/cassandra/developing/cql/index.html[the CQL reference]. A
reasonable way to think of it is as, "SQL minus joins and subqueries, plus collections."

Wondering where to go from here?

  * Join us in #cassandra on the https://s.apache.org/slack-invite[ASF Slack] and ask questions.
  * Subscribe to the Users mailing list by sending a mail to
    user-subscribe@cassandra.apache.org.
  * Subscribe to the Developer mailing list by sending a mail to
    dev-subscribe@cassandra.apache.org.
  * Visit the https://cassandra.apache.org/community/[community section] of the Cassandra website for more information on getting involved.
  * Visit the https://cassandra.apache.org/doc/latest/development/index.html[development section] of the Cassandra website for more information on how to contribute.