Apache Cassandra

Apache Cassandra mixes features of key-value and traditional relational databases. In a conventional relational database, the columns of a table are fixed. In Cassandra, however, rows within the same table can have different columns. Cassandra is, therefore, column-oriented, since it allows a flexible schema for each row. Columns are organized in so-called column families, which are equivalent to tables in relational databases. Joins and subqueries are not possible with Cassandra. Cassandra can be downloaded from http://cassandra.apache.org/download/. We used Cassandra version 3.9 at the time of writing this book. Please refer to http://wiki.apache.org/cassandra/GettingStarted to get started:

1. Run the server from the command line as follows:

   $ bin/cassandra-f
   

2. Create the directories listed in conf/cassandra.yaml or tweak them as follows:

   data_file_directories:
   /tmp/lib/cassandra/data
   commitlog_directory: /tmp/lib/cassandra/commitlog
   saved_caches_directory: /tmp/lib/cassandra...