TOUCH

The TOUCH command in DiceDB is used to update the last access time of one or more keys without modifying their values. This can be particularly useful for cache management, where you want to keep certain keys from expiring by marking them as recently used.

Syntax

TOUCH key [key ...]

Parameters

Parameter	Description	Type	Required
key	The key(s) whose last access time you want to update. You can specify multiple keys separated by spaces.	String	Yes

Return Value

Condition	Return Value
The access time of the key(s) was successfully updated.	integer
The type of key is unsupported.	error

Behaviour

• When the TOUCH command is executed, it will Check whether or not the specified key(s) exists in the database.
• If a key exists, its last access time will be updated to the current time.
• If a key does not exist, it will be ignored.
• The command will return the count of keys that were successfully touched.

Errors

The TOUCH command can raise the following errors:

• WRONGTYPE Operation against a key holding the wrong kind of value: This error occurs if the key exists but is not of a type that supports the TOUCH operation (e.g., a key holding a non-string value).

Example Usage

Single Key

SET mykey "Hello"
TOUCH mykey

In this example, the TOUCH command updates the last access time of the key mykey.

Multiple Keys

SET key1 "value1"
SET key2 "value2"
TOUCH key1 key2 key3

In this example, the TOUCH command attempts to update the last access time for key1, key2, and key3. Since key3 does not exist, it will be ignored. The command will return 2, indicating that two keys were successfully touched.

Invalid usage

Trying to touch key mylist will result in a WRONGTYPE error because mylist is a list, not a string.

LPUSH mylist "element"
TOUCH mylist

Best Practices

• Avoid using the TOUCH command on a large number of keys simultaneously, as it may slow down the server.

Notes

• The TOUCH command only updates the last access time of a key, without modifying its value or other attributes.