HBase - Update Data


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Updating Data using HBase Shell

You can update an existing cell value using the put command. To do so, just follow the same syntax and mention your new value as shown below.

put ‘table name’,’row ’,'Column family:column name',’new value’

The newly given value replaces the existing value, updating the row.

Example

Suppose there is a table in HBase called emp with the following data.

hbase(main):003:0> scan 'emp'
 ROW              COLUMN + CELL
row1 column = personal:name, timestamp = 1418051555, value = raju
row1 column = personal:city, timestamp = 1418275907, value = Hyderabad
row1 column = professional:designation, timestamp = 14180555,value = manager
row1 column = professional:salary, timestamp = 1418035791555,value = 50000
1 row(s) in 0.0100 seconds

The following command will update the city value of the employee named ‘Raju’ to Delhi.

hbase(main):002:0> put 'emp','row1','personal:city','Delhi'
0 row(s) in 0.0400 seconds

The updated table looks as follows where you can observe the city of Raju has been changed to ‘Delhi’.

hbase(main):003:0> scan 'emp'
  ROW          COLUMN + CELL
row1 column = personal:name, timestamp = 1418035791555, value = raju
row1 column = personal:city, timestamp = 1418274645907, value = Delhi
row1 column = professional:designation, timestamp = 141857555,value = manager
row1 column = professional:salary, timestamp = 1418039555, value = 50000
1 row(s) in 0.0100 seconds

Updating Data Using Java API

You can update the data in a particular cell using the put() method. Follow the steps given below to update an existing cell value of a table.

Step 1: Instantiate the Configuration Class

Configuration class adds HBase configuration files to its object. You can create a configuration object using the create() method of the HbaseConfiguration class as shown below.

Configuration conf = HbaseConfiguration.create();

Step 2: Instantiate the HTable Class

You have a class called HTable, an implementation of Table in HBase. This class is used to communicate with a single HBase table. While instantiating this class, it accepts the configuration object and the table name as parameters. You can instantiate the HTable class as shown below.

HTable hTable = new HTable(conf, tableName);

Step 3: Instantiate the Put Class

To insert data into HBase Table, the add() method and its variants are used. This method belongs to Put, therefore instantiate the put class. This class requires the row name you want to insert the data into, in string format. You can instantiate the Put class as shown below.

Put p = new Put(Bytes.toBytes("row1"));

Step 4: Update an Existing Cell

The add() method of Put class is used to insert data. It requires 3 byte arrays representing column family, column qualifier (column name), and the value to be inserted, respectively. Insert data into HBase table using the add() method as shown below.

p.add(Bytes.toBytes("coloumn family "), Bytes.toBytes("column
name"),Bytes.toBytes("value"));
p.add(Bytes.toBytes("personal"),
Bytes.toBytes("city"),Bytes.toBytes("Delih"));

Step 5: Save the Data in Table

After inserting the required rows, save the changes by adding the put instance to the put() method of the HTable class as shown below.

hTable.put(p); 

Step 6: Close HTable Instance

After creating data in HBase Table, close the HTable instance using the close() method as shown below.

hTable.close();

Given below is the complete program to update data in a particular table.

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.util.Bytes;

public class UpdateData{

   public static void main(String[] args) throws IOException {

      // Instantiating Configuration class
      Configuration config = HBaseConfiguration.create();

      // Instantiating HTable class
      HTable hTable = new HTable(config, "emp");

      // Instantiating Put class
      //accepts a row name
      Put p = new Put(Bytes.toBytes("row1"));

      // Updating a cell value
      p.add(Bytes.toBytes("personal"),
      Bytes.toBytes("city"),Bytes.toBytes("Delih"));

      // Saving the put Instance to the HTable.
      hTable.put(p);
      System.out.println("data Updated");

      // closing HTable
      hTable.close();
   }
}

Compile and execute the above program as shown below.

$javac UpdateData.java
$java UpdateData

The following should be the output:

data Updated


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