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GET

Introduction​

In Dragonfly, as well as in Redis and Valkey, the GET command is used to retrieve the value of a key. This is one of the fundamental commands for interacting with string data types and serves as the counterpart to the SET command. It is widely used in caching layers, configuration storage, and other situations where key-value data access is needed.

Syntax​

GET key
  • Time complexity: O(1)
  • ACL categories: @read, @string, @fast

Parameter Explanations​

  • key: The key whose associated value will be retrieved. If the key holds a value other than a string, an error is returned.

Return Values​

  • If the key exists, GET returns the value associated with it as a string.
  • If the key does not exist, nil is returned.

Code Examples​

Basic Example​

Retrieve the value of a key:

dragonfly> SET mykey "Hello, Dragonfly!"
OK
dragonfly> GET mykey
"Hello, Dragonfly!"

Non-Existent Key​

If the key does not exist, GET will return nil:

dragonfly> GET non_existent_key
(nil)

Overwriting a Key​

Setting and then retrieving the updated value of a key:

dragonfly> SET counter "5"
OK
dragonfly> GET counter
"5"
dragonfly> SET counter "10"
OK
dragonfly> GET counter
"10"

Storing JSON-like Data​

In Dragonfly, Redis, or Valkey, the string data type is binary-safe. This means that you can store ASCII strings, unicode strings, or even binary data like an image using the string data type. For instance, you can store JSON-encoded values to model more complex and structured data:

dragonfly> SET user:1001 '{"name": "Alice", "age": 30, "country": "Wonderland"}'
OK
dragonfly> GET user:1001
"{\"name\": \"Alice\", \"age\": 30, \"country\": \"Wonderland\"}"

You can decode this string in your application using your favorite JSON library.

Binary Data Retrieval​

GET also works for values that contain binary data:

dragonfly> SET binary_data "\x00\x01\x02\x03"
OK
dragonfly> GET binary_data
"\x00\x01\x02\x03"

Best Practices​

  • Use the GET command in combination with SET to implement caching mechanisms and session storage efficiently.
  • Ensure keys are named using a consistent, readable convention to avoid key collisions and enhance code readability. For example, user:1001:first_name rather than user1001.

Common Mistakes​

  • Providing a key name that has not been set. This will result in a return of nil, which some developers may not expect.
  • Using GET on a key that holds a non-string data type like lists, sets, or hashes—which will result in an error (WRONGTYPE Operation against a key holding the wrong kind of value).

FAQs​

What happens if the key does not exist?​

If the key does not exist, GET returns nil. It does not return an empty string or an error.

Can I use the GET command to retrieve values from non-string data types?​

No, the GET command is specifically for strings. If used on a key that holds a different data type (e.g., a list or a hash), a WRONGTYPE error will be raised.