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The following page has been changed by MarkMcBride: http://wiki.apache.org/cassandra/DataModel2 ------------------------------------------------------------------------------ Cassandra has a data model that can most easily be thought of as a four or five dimensional hash. The basic concepts are a cluster, which can contain multiple keyspaces. Each keyspace can contain multiple column families. Keyspaces contain multiple rows, which are referenced by keys. These rows contain multiple columns, each of which has a value and a timestamp. Super columns can be thought of as columns that have subcolumns. We'll start from the bottom up, moving from the leaves of Cassandra's data structure (columns) up to the root of the tree (the cluster). - = Columns = + = Columns = The column is the lowest/smallest increment of data. It's a tuple (triplet) that contains a name, a value and a timestamp. @@ -68, +68 @@ = Keyspaces = - A keyspace is the first dimension of the Cassandra hash, and is the container for column families. Keyspaces are roughly equivalent to a schema or database in the RDBMS world. They are the configuration and management point for column families, and is also the structure on which batch inserts are applied. + A keyspace is the first dimension of the Cassandra hash, and is the container for column families. Keyspaces are of roughly the same granularity as a schema or database (i.e. a logical collection of tables) in the RDBMS world. They are the configuration and management point for column families, and is also the structure on which batch inserts are applied. + + = Cluster = + + A cluster is a collection of one or more keyspaces. Cassandra server processes belong to a specific cluster. = Super Columns =
