Learning Objectives

Know HBase interactive shell.
Being able to conduct CRUD operations.

Apache HBase is a distributed column-oriented database built on top of the Hadoop file system. Use HBase when you need random, realtime read/write access to your Big Data. It provides a convenient interactive shell as well as a Java API.

Interactive Shell

You can start the HBase interactive shell using hbase shell command. You will get

HBase Shell; enter 'help<RETURN>' for list of supported commands.
Type "exit<RETURN>" to leave the HBase Shell
Version 0.94.18, rb149f3f0d25c5cd2f195b39fe05d42507fdeabfc, Sat May 23 00:09:16 GMT 2015

hbase(main):001:0>

To exit the interactive shell, type exit or <ctrl+c>.

Create

The syntax to create a table in HBase shell is shown below.

create 'table name', 'column family'

Let's create a table called hospital with two column families id and value.

hbase(main):002:0> create 'hospital', 'id', 'value'

And it will give you the following output.

0 row(s) in 1.1620 seconds

Update

List table(s)

hbase(main):003:0> list
TABLE
hospital
1 row(s) in 0.0180 seconds

Describe and alter table

The describe command returns the description of the table.

hbase(main):004:0> describe 'hospital'
'hospital', {NAME => 'id', DATA_BLOCK_ENCODING => 'NONE', BLOOMFILTER => 'NONE', REPLICATION_SCOPE => true                                                    
  '0', VERSIONS => '3', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => '2147483647', KEEP_DELETED_                                                         
 CELLS => 'false', BLOCKSIZE => '65536', IN_MEMORY => 'false', ENCODE_ON_DISK => 'true', BLOCKCACHE =>                                                         
  'true'}, {NAME => 'value', DATA_BLOCK_ENCODING => 'NONE', BLOOMFILTER => 'NONE', REPLICATION_SCOPE =                                                         
 > '0', VERSIONS => '3', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => '2147483647', KEEP_DELETED                                                         
 _CELLS => 'false', BLOCKSIZE => '65536', IN_MEMORY => 'false', ENCODE_ON_DISK => 'true', BLOCKCACHE =                                                         
 > 'true'}                                                                                                                                                     
1 row(s) in 0.0350 seconds

This shows some basic information for each column family. For example, the id column family has block size 65536 and keeps at most 3 versions for each cell (distinguish by timestamp).

We can alter the setting by using alter. But we need to first disable the table.

hbase(main):005:0> disable 'hospital'
hbase(main):006:0> alter 'hospital', {NAME => 'id', VERSIONS => 5}

Don't forget to re-enable after changing the setting.

hbase(main):007:0> enable 'hospital'

Put data

Using put command, you can insert rows into a table. Its syntax is as follows:

put 'table name', 'row key', 'colfamily:colname', 'value'

For example, let's put a record of a paitent-id.

hbase(main):008:0> put 'hospital', 'row1', 'id:patient', 'patient-id-1'
0 row(s) in 0.0140 seconds

This puts the value patient-id-1 in row row1 and column patient (within the column family id). Let's put some more records.

hbase(main):009:0> put 'hospital', 'row1', 'id:event', 'event-id-1'
hbase(main):010:0> put 'hospital', 'row1', 'value:value', '1'
hbase(main):011:0> put 'hospital', 'row2', 'id:event', 'event-id-2'

Read

Cluster status

Checking the status of the cluster

hbase(main):001:0> status
(may have some debug messages)
2 servers, 0 dead, 1.0000 average load

Table data

Using the scan command, you can get the table data.

hbase(main):012:0> scan 'hospital'
ROW            COLUMN+CELL
 row1          column=id:event, timestamp=1436623001980, value=event-id-1
 row1          column=id:patient, timestamp=1436622532169, value=patient-id-1
 row1          column=value:value, timestamp=1436622642925, value=1
 row2          column=id:event, timestamp=1436623003694, value=event-id-2
2 row(s) in 0.0130 seconds

If you only want to know the number of rows, you can use

hbase(main):013:0> count 'hospital'
2 row(s) in 0.0130 seconds

Using the get command, you can get a single row of data at a time.

hbase(main):014:0> get 'hospital', 'row1' 
COLUMN                                   CELL
 id:event           timestamp=1436623001980, value=event-id-1
 id:patient         timestamp=1436622532169, value=patient-id-1
 value:value        timestamp=1436622642925, value=1
3 row(s) in 0.0270 seconds

We can further specify the column that we want to retrieve.

hbase(main):015:0> get 'hospital', 'row1', {COLUMN => 'id:patient'}
 id:patient       timestamp=1436622532169, value=patient-id-1
 1 row(s) in 0.9730 seconds

Delete

Delete cell

You can delete a specific cell in a table by the delete command

hbase(main):016:0> delete 'hospital', 'row1', 'id:event'
0 row(s) in 0.0100 seconds

To delete all the cells in a row, use the deleteall command

hbase(main):017:0> deleteall 'hospital', 'row1'
0 row(s) in 0.0110 seconds

Drop table

Using the drop command, you can delete a table. Before dropping a table, you have to disable it.

hbase(main):018:0> disable 'hospital'
0 row(s) in 1.1000 seconds

hbase(main):019:0> drop 'hospital'