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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "Hbase/DesignOverview" by EvgenyRyabitskiy
Date Thu, 02 Apr 2009 14:37:50 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The following page has been changed by EvgenyRyabitskiy:
http://wiki.apache.org/hadoop/Hbase/DesignOverview

------------------------------------------------------------------------------
  [[Anchor(datamodel)]]
  = Data Model =
  
- Applications store data rows in labeled tables. A data row has a sortable row key and an
arbitrary number of columns. The table is stored sparsely, so that rows in the same table
can have widely varying numbers of columns. 
+ Applications store data rows in labeled tables. A data row has a sortable row key and an
arbitrary number of columns. The table is stored sparsely, so that rows in the same table
can have widely varying numbers of columns.
+ 
+ HBase is three dimensional sorted map. It maps from Cartesian product of row key, column
key and a timestamp to cell value:
+ 
+ (row:byte[] x column:byte[] x timestamp:Long) -> byte[]
  
  A column name has the form ''"<family>:<label>"'' where <family> and <label>
can be arbitrary byte arrays. A table enforces its set of <family>s (called ''"column
families"''). Adjusting the set of families is done by performing administrative operations
on the table. However, new <label>s can be used in any write operation without pre-announcing
it. HBase stores column families physically close on disk, so the items in a given column
family should have roughly the same read/write characteristics and contain similar data.
  

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