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Sunday, 12 February 2017

HBase Drop Table Tutorial


Dropping a Table using HBase Shell
     Using the drop command, you can delete a table. Before dropping a table, you have to disable it.
hbase> disable 'emp' 
0 row(s) in 1.2530 seconds 

hbase> drop 'emp'
0 row(s) in 0.4045 seconds
     Verify whether the table is deleted using the exists command.
hbase> exists 'emp'
Table emp does not exist
0 row(s) in 0.0842 seconds
drop_all
     This command is used to drop the tables matching the “regex” given in the command. Its syntax is as follows:
hbase> drop_all ‘a.*’
Note
     Before dropping a table, you must disable it.
Example
     Assume there are tables named Ashok, Ashwin, Aslam, Asha, and Ashwini.
hbase> list
ashok
ashwin
aslam
asha
ashwini

5 row(s) in 0.0160 seconds
    All these tables start with the letters as. First of all, let us disable all these tables using the disable_all command as shown below.
hbase> disable_all 'as.*'
ashok
ashwin
aslam
asha
ashwini

Disable the above 5 tables (y/n)?
y
5 tables successfully disabled
Disable a Table Using Java API
package com.ashok.hbase;

import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.MasterNotRunningException;
import org.apache.hadoop.hbase.client.HBaseAdmin;

public class DisableTable {

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

      // Instantiating configuration class
      Configuration conf = HBaseConfiguration.create();
 
      // Instantiating HBaseAdmin class
      HBaseAdmin admin = new HBaseAdmin(conf);

      // Verifying weather the table is disabled
      Boolean bool = admin.isTableDisabled("emp");
      System.out.println(bool);

      // Disabling the table using HBaseAdmin object
      if(!bool){
         admin.disableTable("emp");
         System.out.println("Table disabled successfully");
      }
   }
}

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