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From Apache Wiki <>
Subject [Cassandra Wiki] Update of "DataModel2" by MarkR
Date Tue, 18 Aug 2009 07:24:42 GMT
Dear Wiki user,

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The following page has been changed by MarkR:

The comment on the change is:
Clarify timestamp

  All values are supplied by the client, including the timestamp.  This means that clocks
in the Cassandra environment should be synchronized, as these timestamps are used for conflict
resolution.  In many cases the timestamp is not used in client applications, and it becomes
convenient to think of a column as a name/value pair. For the remainder of this document,
timestamps will be elided for readability.  It is also worth noting the name and value are
binary values, although in many applications they are UTF8 serialized strings.
+ Timestamps can be anything you like, but milliseconds since 1970 is a convention, as returned
by System.getTimeMillis() in Java. Whatever you use, it must be consistent across the application
otherwise earlier changes may overwrite newer ones.
  = Column Families =
  A column family is a container for columns.  You define columns in your storage-conf.xml
file, and cannot modify them (or add new column families) without restarting your Cassandra
process.  A column family holds an ordered list of columns, which you can reference by the
column name.  A JSON representation would be

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