Append Operation in Memcached using C# (Detailed Guide w/ Code Examples)

Use Case(s)

The append operation in memcached is primarily used to add or concatenate additional data to an existing key-value pair. This can be useful when you want to update the value of a specific key without having to read its current value (to reduce network overhead).

Code Examples

We'll be using EnyimMemcached, a popular .NET client for memcached, for these examples.

1. Setting up and appending values

var config = new MemcachedClientConfiguration();
config.AddServer("localhost", 11211);
using (var client = new MemcachedClient(config))
{
    //Set a key with initial value
    client.Store(StoreMode.Set, "key1", "value1");
    
    //Append data to the existing key
    bool appendResult = client.Append("key1", ",appendedValue");
    Console.WriteLine($"Append Result: {appendResult}");
    
    //Get the updated value
    var updatedValue = client.Get<string>("key1");
    Console.WriteLine($"Updated Value: {updatedValue}");
}

In this example, we first set an initial value ("value1") for a key ("key1"). We then append a string (",appendedValue") to this key. The final output would be "value1,appendedValue".

2. Handle append failure

using (var client = new MemcachedClient(config))
{
    //Append data to non-existing key
    bool appendResult = client.Append("nonexistingKey", ",appendedValue");
    Console.WriteLine($"Append Result: {appendResult}");
}

In this case, append operation will fail because it's attempted on a non-existing key. The append operation does not create a new key.

Best Practices

• Only use append operations for cases where reading the existing value, updating it on client side and then writing it back to memcached is not efficient.
• Be aware that memcached does not support appending complex objects or serialized data out of the box. Appending works best with string data.

Common Mistakes

• Attempting to append to a non-existent key. The append operation doesn't create a new key; it only adds to an existing one.
• Trying to append complex objects or serialized data. The append operation in Memcached is designed to work primarily with simple string values.

FAQs

Q: Can I append complex objects or serialized data using memcached?

A: No, you can't directly append complex objects or serialized data as memcached supports append operation primarily for simple string values.