Hbase shell and Commands

Hbase Install

$ mkdir hbase-install
$ cd hbase-install
$ wget http://apache.claz.org/hbase/hbase-0.92.1/hbase-0.92.1.tar.gz
$ tar xvfz hbase-0.92.1.tar.gz
$HBASE_HOME/bin/start-hbase.sh

configuration changes in Hbase<property>
<name>hbase.rootdir</name>
<value>file:///home/user/myhbasedirectory/</value>
</property>

$ hbase shell
hbase(main):001:0> list
TABLE
0 row(s) in 0.5710 seconds

Create a table
hbase(main):002:0> create 'mytable', 'cf'
hbase(main):003:0> list
TABLE
mytable
1 row(s) in 0.0080 seconds

WRITING DATA
hbase(main):004:0> put 'mytable', 'first', 'cf:message', 'hello HBase'

READING DATA
hbase(main):007:0> get 'mytable', 'first'
hbase(main):008:0> scan 'mytable'

describe table
hbase(main):003:0> describe 'users'
DESCRIPTION ENABLED
{NAME => 'users', FAMILIES => [{NAME => 'info', true ,BLOOMFILTER => 'NONE', REPLICATION_SCOPE => '0 , COMPRESSION => 'NONE', VERSIONS => '3', TTL=> '2147483647',
BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE => 'true'}]}
1 row(s) in 0.0330 seconds

Configurable block size
hbase(main):002:0> create 'mytable',{NAME => 'colfam1', BLOCKSIZE => '65536'}

Block cache
workloads don’t benefit from putting data into a read cache—for instance, if a certain table or column family in a table is only accessed for sequential scans or isn’t
accessed a lot and you don’t care if Gets or Scans take a little longer.By default, the block cache is enabled. You can disable it at the time of table creation
or by altering the table:
hbase(main):002:0> create 'mytable',{NAME => 'colfam1', BLOCKCACHE => 'false’}

Aggressive caching
You can choose some column families to have a higher priority in the block cache (LRU cache). This comes in handy if you expect more random reads on one column family compared to another. This configuration is also done at table-instantiation time:
hbase(main):002:0> create 'mytable',
{NAME => 'colfam1', IN_MEMORY => 'true'}
The default value for the IN_MEMORY parameter is false.

Bloom filters
hbase(main):007:0> create 'mytable',{NAME => 'colfam1', BLOOMFILTER => 'ROWCOL'}
The default value for the BLOOMFILTER parameter is NONE. A row-level bloom filter is enabled with ROW, and a qualifier-level bloom filter is enabled with ROWCOL. The rowlevel bloom filter checks for the non-existence of the particular rowkey in the block,and the qualifier-level bloom filter checks for the non-existence of the row and column qualifier combination. The overhead of the ROWCOL bloom filter is higher than that of the ROW bloom filter.

TTL (Time To Live)
can set the TTL while creating the table like this:
hbase(main):002:0> create 'mytable', {NAME => 'colfam1', TTL => '18000'}
This command sets the TTL on the column family colfam1 as 18,000 seconds = 5 hours. Data in colfam1 that is older than 5 hours is deleted during the next major compaction.

Compression
can enable compression on a column family when creating tables like this:
hbase(main):002:0> create 'mytable',
{NAME => 'colfam1', COMPRESSION => 'SNAPPY'}
Note that data is compressed only on disk. It’s kept uncompressed in memory (Mem-Store or block cache) or while transferring over the network.

Cell versioning
Versions are also configurable at a column family level and can be specified at
the time of table instantiation:
hbase(main):002:0> create 'mytable', {NAME => 'colfam1', VERSIONS => 1}
hbase(main):002:0> create 'mytable',
{NAME => 'colfam1', VERSIONS => 1, TTL => '18000'}
hbase(main):002:0> create 'mytable', {NAME => 'colfam1', VERSIONS => 5,
MIN_VERSIONS => '1'}

Description of a table
hbase(main):004:0> describe 'follows'
DESCRIPTION ENABLED
{NAME => 'follows', coprocessor$1 => 'file:///U true users/ndimiduk/repos/hbaseia twitbase/target/twitbase-1.0.0.jar|HBaseIA.TwitBase.coprocessors.FollowsObserver|1001|', FAMILIES => [{NAME => 'f', BLOOMFILTER => 'NONE', REPLICATION_SCOPE =>'0', VERSIONS => '1', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => '2147483647', BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE => 'true'}]}
1 row(s) in 0.0330 seconds

Tuning HBase
hbase(main):003:0> help 'status'

SPLITTING TABLES
hbase(main):019:0> split 'mytable' , 'G'
Alter table
hbase(main):020:0> alter 't', NAME => 'f', VERSIONS => 1

TRUNCATING TABLES
hbase(main):023:0> truncate 't'
Truncating 't' table (it may take a while):
- Disabling table...
- Dropping table...
- Creating table...
0 row(s) in 14.3190 seconds