add operation in Memcached using Ruby is commonly used when you want to store a value only if the server doesn't already hold data for this key. This can be particularly useful when initializing some critical values or when working with distributed systems where multiple processes might attempt to set a value concurrently.
Here is how to use the
add function in Ruby with the 'dalli' gem, a popular choice for interfacing with Memcached.
Make sure you have installed the 'dalli' gem:
Here's a simple example of using
In this example, the initial value
'bar' for key
'foo' remains intact because the
add operation will not overwrite an existing key.
addwhen you're unsure whether a key exists and do not want to overwrite it.
add. It returns
trueif it successfully added the item,
falseotherwise. Ignoring this can lead to incorrect assumptions about the state of your cache.
Q: What happens if I use
add with a key that already exists in Memcached?
A: If the key already exists,
add will not update the value and will return
false. The existing key-value pair will remain as it is.
Q: Is Memcached data persistent? A: No, Memcached is not a persistent data store. It's a caching system, which means data stored in it could disappear at any time (e.g., eviction due to low memory or server restart).