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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.
