====== hbase ======

  * [[Hadoop]]
  * [[hdfs]]

  * [[https://hbase.apache.org/book.html|Apache HBase Reference Guide]]
  * [[https://wiki.apache.org/hadoop/Hbase/Shell|hbase shell commands]]
  * [[https://learnhbase.wordpress.com/2013/03/02/hbase-shell-commands/|Learn HBase: shell commands]]

Start REST server:

<code>
hbase-daemon.sh start rest
</code>

==== hbase shell ====

To script stuff through hbase shell, there are two ways. One is to pipe things directly:

<code>
echo list | hbase shell
</code>

And the other is to write a script:

<code>
echo list > test_script
hbase shell test_script
</code>

To save history, add this to ''.irbrc'':

<code>
require 'irb/ext/save-history'
IRB.conf[:SAVE_HISTORY] = 100
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb_history"
Kernel.at_exit do
    IRB.conf[:AT_EXIT].each do |i|
        i.call
    end
end
</code>

** Display status: **

<code>
echo status | hbase shell
5 servers, 0 dead, 2365.2000 average load
</code>

** List tables: **

<code>
echo list | hbase shell
</code>

** Describe the table: **

<code>
echo "describe 'table'" | hbase shell
</code>

==== hbase backups ====

** Exporting a table **

From the docs: "Export is a utility that will dump the contents of table to HDFS in a sequence file." [[http://hbase.apache.org/book.html#_export|Source]]

<code>
hbase org.apache.hadoop.hbase.mapreduce.Export <tablename> <outputdir> [<versions> [<starttime> [<endtime>]]]
</code>

For example, exporting table ''table_name'':

<code>
hbase org.apache.hadoop.hbase.mapreduce.Export table_name /tmp/table_name
</code>

** Importing a table: **

From the docs: "Import is a utility that will load data that has been exported back into HBase." [[http://hbase.apache.org/book.html#_import|Source]]

<code>
hbase -Dhbase.import.version=0.94 org.apache.hadoop.hbase.mapreduce.Import <tablename> <inputdir>
</code>

==== TTL ====

Changing TTL: "ColumnFamilies can set a TTL length in seconds, and HBase will automatically delete rows once the expiration time is reached. This applies to //all// versions of a row - even the current one. The TTL time encoded in the HBase for the row is specified in UTC." [[https://hbase.apache.org/book.html#ttl|Source]]

Change the TTL (time-to-live), and compact the data, which will erase anything older than that, in this case, one week:

<code>
alter 'table', { TTL => 604800 }
major_compact 'table'
</code>