The add
command in Memcached is used when you want to store a key-value pair, but only if the server doesn't already hold data for this key. This can be particularly useful in scenarios where you want to avoid overwriting existing data.
Here is an example of how to use the add
function using the pymemcache
library in Python:
from pymemcache.client.base import Client client = Client(('localhost', 11211)) # Adding a new key-value pair result = client.add('my_key', 'my_value') print(result) # it will print True if the key was added successfully, False otherwise.
In this example, we're connecting to a Memcached server running on localhost
and default port 11211
. We then try to add a new key-value pair ('my_key', 'my_value'). If 'my_key' doesn't already exist, it will be added, and the method will return True
.
If we try to add the same key again, the operation will fail:
result = client.add('my_key', 'another_value') print(result) # it will print False because 'my_key' already exists.
add
method is designed to avoid overwriting existing keys. Thus, ensure your application logic takes into account that keys should be unique.add
failures: Since add
returns False
when it fails to add a key (because it's already there), make sure your code handles such cases appropriately.add
will always succeed: If the add
operation returns False
, it means the key already exists. Your code should handle this scenario correctly and not assume that the add
operation will always succeed.1. What's the difference between 'set' and 'add' in Memcached?
The 'set' command will always store the value, regardless of whether the key already exists or not. On the other hand, 'add' will only store the value if the key does not exist.
2. What happens if I try to add a key that already exists?
If you try to add a key that already exists using the add
method, the operation will simply fail and return False
.
Dragonfly is fully compatible with the Redis ecosystem and requires no code changes to implement.