HBase useful commands

1) Connect to HBase. Connect to your running instance of HBase using the hbase shell command, located in the bin/ directory of your HBase install.

$ ./bin/hbase shell 

2) Create a table. Use the create command to create a new table. You must specify the table name and the ColumnFamily name.

hbase(main):001:0> create 'test', 'cf' 
0 row(s) in 0.4170 seconds 

=> Hbase::Table - test

3) List Information About your Table.

hbase(main):002:0> list 'test'
1 row(s) in 0.0180 seconds 

=> ["test"]

4) Put data into your table. Here, we insert three values, one at a time. The first insert is at row1, column cf:a, with a value of value1. Columns in HBase are comprised of a column family prefix, cf in this example, followed by a colon and then a column qualifier suffix, a in this case.

hbase(main):003:0> put 'test', 'row1', 'cf:a', 'value1' 
0 row(s) in 0.0850 seconds 

hbase(main):004:0> put 'test', 'row2', 'cf:b', 'value2' 
0 row(s) in 0.0110 seconds 

hbase(main):005:0> put 'test', 'row3', 'cf:c', 'value3' 
0 row(s) in 0.0100 seconds

5) Scan the table for all data at once. One of the ways to get data from HBase is to scan. Use the scan command to scan the table for data. You can limit your scan, but for now, all data is fetched.

hbase(main):006:0> scan 'test' 
 row1 column=cf:a, timestamp=1421762485768, value=value1
 row2 column=cf:b, timestamp=1421762491785, value=value2
 row3 column=cf:c, timestamp=1421762496210, value=value3
3 row(s) in 0.0230 seconds

6) Get a single row of data.

hbase(main):007:0> get 'test', 'row1'
 cf:a timestamp=1421762485768, value=value1 

1 row(s) in 0.0350 seconds

7) Disable a table. If you want to delete a table or change its settings, as well as in some other situations, you need to disable the table first, using the disable command. You can re-enable it using the enable command.

hbase(main):008:0> disable 'test' 
0 row(s) in 1.1820 seconds 

hbase(main):009:0> enable 'test' 
0 row(s) in 0.1770 seconds

8) Disable the table again if you tested the enable command above:

hbase(main):010:0> disable 'test' 
0 row(s) in 1.1820 seconds

9) Drop the table.

hbase(main):011:0> drop 'test' 
0 row(s) in 0.1370 seconds

10) Backup and restore to S3:

10.1) BackUp:

hadoop jar /home/hadoop/lib/hbase.jar emr.hbase.backup.Main --backup --backup-dir s3://your-bucket/backups/j-XXXX

10.2) Restore:

hadoop jar /home/hadoop/lib/hbase.jar emr.hbase.backup.Main --restore --backup-dir s3://your-bucket/backup-hbase/j-XXXX'

10.3) Import:

hbase org.apache.hadoop.hbase.mapreduce.Import test s3n://your-bucket/backup-hbase/j-XXXX

11) Backup and Restore with Distcp and S3distCp:

11.1) Using Distcp method to backup to S3:

hadoop distcp hdfs://ec2-52-16-22-167.eu-west-1.compute.amazonaws.com:9000/hbase/ s3://your-bucket/hbase/201502280715/

11.2) Using Distcp to backup to another cluster:

hadoop distcp hdfs://ec2-52-16-22-167.eu-west-1.compute.amazonaws.com:9000/hbase/ hdfs://ec2-54-86-229-249.compute-1.amazonaws.comec2-2:9000/hbase/

11.3) Using S3distcp method to backup to S3:

hadoop jar ~/lib/emr-s3distcp-1.0.jar --src hdfs:///hbase/ --dest s3://your-bucket/hbase/201502280747/

Christiaan Barnard y René Favaloro

Hoy fuimos al Christiaan Barnard Memorial Hospital, e inmediatamente me acordé de René Favaloro, pensando si esas dos eminencias de la cardiología serían contemporáneos…

Revolviendo en internet encontré esta foto.


Comparto una profunda admiración por estos dos científicos del corazón (en todo el sentido de la palabra).

Hive: Extracting JSON fields

Handling JSON files with Hive is not always an easy task.

If you need to extract some specific fields from a structured JSON, we have some alternatives:

There are two UDF functions that are usually helpful on this cases: ‘get_json_object’ and ‘json_tuple’. These functions allows you to access json fields from Hive without installing additional libraries.





To navigate JSON structure with get_json_object, the entire JSON file has to be mapped as string.

As example:

1) Create the external table as string:

CREATE EXTERNAL TABLE json_table (str string) LOCATION 's3://mybucket/input/jsonserde' ;

2) select field[0] from store.fruit field:

select get_json_object(json_table.str, '$.store.fruit\[0]') as MyField from json_table;