Deleting keys in Redis can be a costly operation, especially when dealing with a large number of keys or large-size values. It's important to understand how it can impact performance.
): This is a simple operation that will immediately delete a key from Redis. It's an O(1)
complexity operation, meaning it takes constant time regardless of the number of keys in the database. However, if the value stored at the key is a large data structure, the operation could take more time due to memory management overhead.UNLINK
): Introduced in Redis 4.0, UNLINK
is a command that deletes keys in a non-blocking manner. While DEL
frees the memory associated with a key synchronously, UNLINK
does this asynchronously. Meaning, it returns control to the client before the memory is actually freed, thereby causing a less immediate impact on performance.KEYS
): When you need to delete multiple keys matching a certain pattern, you might use the KEYS
command to find these keys and then delete them using DEL
. However, this operation can block the server for a long time if the server has a lot of data, as KEYS
scans the entire key space.This script uses Lua scripting feature of Redis to delete keys matching a pattern in a single operation, which can be faster than multiple round trips. However, this can still cause high CPU load and should be used carefully.
): A more performance-friendly way to delete keys matching a pattern is by using the SCAN
command with DEL
retrieves keys in a cursor-based iterative manner, not blocking the server like KEYS
.Take note, frequent deletions of large amounts of data could lead to memory fragmentation over time. This might degrade overall Redis performance as it could increase memory usage or slow down certain operations.