Cassandra - Drop Index


Advertisements


Dropping an Index using Cqlsh

You can drop an index using the command DROP INDEX. Its syntax is as follows:

DROP INDEX <identifier>

Given below is an example to drop an index of a column in a table. Here we are dropping the index of the column name in the table emp.

cqlsh:tp> drop index name;

Dropping an Index using Java API

You can drop an index of a table using the execute() method of Session class. Follow the steps given below to drop an index from a table.

Step1: Create a Cluster Object

Create an instance of Cluster.builder class of com.datastax.driver.core package as shown below.

//Creating Cluster.Builder object
Cluster.Builder builder1 = Cluster.builder();

Add a contact point (IP address of the node) using the addContactPoint() method of Cluster.Builder object. This method returns Cluster.Builder.

//Adding contact point to the Cluster.Builder object
Cluster.Builder builder2 = build.addContactPoint( "127.0.0.1" );

Using the new builder object, create a cluster object. To do so, you have a method called build() in the Cluster.Builder class. The following code shows how to create a cluster object.

//Building a cluster
Cluster cluster = builder.build();

You can build a cluster object using a single line of code as shown below.

Cluster cluster = Cluster.builder().addContactPoint("127.0.0.1").build();

Step 2: Create a Session Object

Create an instance of Session object using the connect() method of Cluster class as shown below.

Session session = cluster.connect( );

This method creates a new session and initializes it. If you already have a keyspace, then you can set it to the existing one by passing the KeySpace name in string format to this method as shown below.

Session session = cluster.connect(“ Your keyspace name ” );

Here we are using the KeySpace named tp. Therefore, create the session object as shown below.

Session session = cluster.connect(“ tp” );

Step 3: Execute Query

You can execute CQL queries using the execute() method of Session class. Pass the query either in string format or as a Statement class object to the execute() method. Whatever you pass to this method in string format will be executed on the cqlsh.

In the following example, we are dropping an index “name” of emp table. You have to store the query in a string variable and pass it to the execute() method as shown below.

//Query
String query = "DROP INDEX user_name;";
session.execute(query);

Given below is the complete program to drop an index in Cassandra using Java API.

import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.Session;

public class Drop_Index {

   public static void main(String args[]){
     
      //Query
      String query = "DROP INDEX user_name;";
 
      //Creating cluster object
      Cluster cluster = Cluster.builder().addContactPoint("127.0.0.1").build();.
 
      //Creating Session object
      Session session = cluster.connect("tp"); 
 
      //Executing the query
      session.execute(query);
      
      System.out.println("Index dropped");
   }
}

Save the above program with the class name followed by .java, browse to the location where it is saved. Compile and execute the program as shown below.

$javac Drop_index.java
$java Drop_index

Under normal conditions, it should produce the following output:

Index dropped


Advertisements