HGET

The HGET command in DiceDB is used to retrieve the value associated with a specified field within a hash stored at a given key. If the key or the field does not exist, the command returns a nil value.

Syntax

HGET key field

Parameters

Parameter	Description	Type	Required
key	The key of the hash from which the field’s value is to be retrieved.	String	Yes
field	The field within the hash whose value is to be retrieved.	String	Yes

Return Values

Condition	Return Value
Field exists in the hash	String (value of the field)
Key does not exist or field not present	nil
Wrong data type	(error) WRONGTYPE Operation against a key holding the wrong kind of value
Incorrect Argument Count	(error) ERR wrong number of arguments for 'hget' command

Behaviour

When the HGET command is executed, DiceDB performs the following steps:

• It checks if the key exists in the database.
• If the key exists and is of type hash, it then checks if the specified field exists within the hash.
• If the field exists, it retrieves and returns the value associated with the field.
• If the key does not exist or the field is not present in the hash, it returns nil.

Errors

1. Non-hash type or wrong data type:

   • Error Message: (error) WRONGTYPE Operation against a key holding the wrong kind of value
   • Occurs if key holds a non-hash data structure.

2. Incorrect Argument Count:

   • Error Message: (error) ERR wrong number of arguments for 'hget' command
   • Occurs if the command is not provided with the correct number of arguments (i.e., fewer than two).

Example Usage

Retrieving a value from a hash

127.0.0.1:7379> HSET user:1000 name "John Doe"
(integer) 1
127.0.0.1:7379> HSET user:1000 age "30"
(integer) 1
127.0.0.1:7379> HGET user:1000 name
"John Doe"

Field does not exist

127.0.0.1:7379> HGET user:1000 email
(nil)

Key does not exist

127.0.0.1:7379> HGET user:2000 name
(nil)

Key is not a hash

127.0.0.1:7379> SET user:3000 "Not a hash"
OK
127.0.0.1:7379> HGET user:3000 name
(error) WRONGTYPE Operation against a key holding the wrong kind of value

Invalid Usage

127.0.0.1:7379> SET product:2000 "This is a string"
OK
127.0.0.1:7379> HGET product:2000 name
(error) WRONGTYPE Operation against a key holding the wrong kind of value

127.0.0.1:7379> HGET product:2000
(error) ERR wrong number of arguments for 'hget' command

127.0.0.1:7379> HGET product:2000 name name2
(error) ERR wrong number of arguments for 'hget' command

Notes

• The HGET command is a read-only command and does not modify the hash or any other data in the DiceDB database.

By understanding the HGET command, you can efficiently retrieve values from hashes stored in your DiceDB database, ensuring that your application can access the necessary data quickly and reliably.