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cassandra 知识
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cassandra

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Apache Cassandra

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

http://wiki.apache.org/cassandra/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.

http://wiki.apache.org/cassandra/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 http://cassandra.apache.org/[the Apache Cassandra web site].

Requirements

. Java >= 1.8 (OpenJDK and Oracle JVMS have been tested) . Python 2.7 (for cqlsh)

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 http://cassandra.apache.org/doc/latest/getting_started/[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

Note for Windows users: to install Cassandra as a service, download http://commons.apache.org/daemon/procrun.html[Procrun], set the PRUNSRV environment variable to the full path of prunsrv (e.g., C:\procrun\prunsrv.exe), and run "bin\cassandra.bat install". Similarly, "uninstall" will remove the service.

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 2.2.0 | Cassandra 1.2.0 | CQL spec 3.0.0 | Thrift protocol 19.35.0] 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 SCHEMA 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 http://cassandra.apache.org/doc/latest/cql/[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?