Question

What is Memcached replace command?

Answer 1

Memcached replace command is used to replace the value of an existing key. If the key does not exist, then it gives the output NOT_STORED.

Syntax

The basic syntax of Memcached replace command is as shown below −

replace key flags exptime bytes [noreply]
value

The keywords in the syntax are as described below −

• key − It is the name of the key by which data is stored and retrieved from Memcached.

• flags − It is the 32-bit unsigned integer that the server stores with the data provided by the user, and returns along with the data when the item is retrieved.

• exptime − It is the expiration time in seconds. 0 means no delay. If exptime is more than 30 days, Memcached uses it as a UNIX timestamp for expiration.

• bytes − It is the number of bytes in the data block that needs to be stored. This is the length of the data that needs to be stored in the Memcached.

• noreply (optional) − It is a parameter that informs the server not to send any reply.

• value − It is the data that needs to be stored. The data needs to be passed on the new line after executing the command with the above options.

Output

The output of the command is as shown below −

STORED

• STORED indicates success.

• NOT_STORED indicates the data is not stored in Memcached.

Example

In the following example, we use ‘key’ as the key and store memcached in it with an expiration time of 900 seconds. After this, the same key is replaced with the value ‘redis’.

add key 0 900 9
memcached
STORED
get key
VALUE key 0 9
memcached
END
replace key 0 900 5
redis
get key
VALUE key 0 5
redis
END

Replace Data Using Java Application

To replace data in a Memcached server, you need to use the Memcached replace method.

Example

import net.spy.memcached.MemcachedClient;
public class MemcachedJava {
   public static void main(String[] args) {
      
      // Connecting to Memcached server on localhost
      MemcachedClient mcc = new MemcachedClient(new
      InetSocketAddress("127.0.0.1", 11211));
      System.out.println("Connection to server sucessfully");
      System.out.println("set status:"+mcc.set("tutorialspoint", 900, "memcached").done);
      
      // Get value from cache
      System.out.println("Get from Cache:"+mcc.get("tutorialspoint"));
      
      // now replace the existing data
      System.out.println("Replace cache:"+mcc.replace("tutorialspoint", 900, "redis").done);
      
      // get the updated data
      System.out.println("Get from Cache:"+mcc.get("tutorialspoint"));
   }
}

Output

On compiling and executing the program, you get to see the following output −

Connection to server successfully
set status:true
Get from Cache:memcached
Replace cache:true
Get from Cache:redis