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GETSET

Sets the value of a key and returns the old value stored at the key.

Syntax​

GETSET key value

Parameters​

  • key: The name of the key whose value you want to set.
  • value: The new value to set at the specified key.

Details​

  • Available since: 1.0.0
  • Time complexity: O(1)
  • ACL categories: @write, @string, @fast

The GETSET command sets the value of a key to the specified value and returns the old value stored at the key. If the key did not previously exist, GETSET returns nil. This command is useful for atomically setting a value while retrieving the previous value in a single operation.

Examples​

Basic Usage​

Assume we have a key called mykey with the value "Hello":

SET mykey "Hello"

To set a new value "World" and get the old value:

GETSET mykey "World"

This will return:

"Hello"

After running this command, the value of mykey will be "World".

Handling a Non-Existent Key​

If the key does not exist and you use GETSET:

GETSET newkey "FirstValue"

This will return:

(nil)

The key newkey will now be set to "FirstValue".

Edge Cases​

  • If the key does not exist, GETSET returns nil and sets the key to the specified value.
  • If the key exists but is not a string, an error is returned.

RESP2/RESP3 Reply​

  • Bulk string reply: the old value stored at the key, or nil if the key did not exist.