replace operation in Memcached is used when you want to modify the value of an existing key. This operation is only successful if the given key already exists in Memcached. Common use cases include:
Ruby's Dalli gem is often used to interface with Memcached. Here's how to use the replace function:
In this example, we first create a connection to the Memcached server using Dalli. We then set the initial value of the key 'foo' to be 'bar'. We then replace the same 'foo' key's value with 'baz'.
Note: If the key does not exist,
replace will raise an error.
In this second example, attempting to replace a non-existent key raises a
replacewhen you're sure that the key exists. If unsure, consider using
add, which are more forgiving operations.
Dalli::DalliErrorthat may result from trying to replace a non-existent key.
replaceon a non-existing key. This will result in an error and may cause your application to crash if not handled properly.
Q: What's the difference between 'set' and 'replace'? A: The 'set' operation will add a new entry whether or not the key already exists whereas the 'replace' operation only modifies the value of an existing key. If the key does not exist, 'replace' will raise an error.