HMGET

The HMGET command in DiceDB is used to retrieve the values of one or more specified fields from a hash. It allows efficient fetching of specific fields from a hash without retrieving the entire hash.

Syntax

HMGET key field [field ...]

Parameters

Parameter	Description	Type	Required
key	The name of the hash.	String	Yes
field	The field within the hash to retrieve the value for.	String	Yes
[field ...]	Additional fields to retrieve from the hash.	String	No

Return Values

Condition	Return Value
Field exists	String (The value of the field)
Field does not exist	nil
Multiple fields retrieved	List of values for each field
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 'hmget' command

Behaviour

When the HMGET command is executed, the following actions occur:

• The specified fields are fetched from the hash.
• If a field exists, its value is returned.
• If a field does not exist, nil is returned for that field.
• The command returns a list of values, corresponding to each field requested.

Errors

The HMGET command can raise errors in the following scenarios:

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 'hmget' command
   • Occurs if the command is not provided with the correct number of arguments (i.e., fewer than two).

Example Usage

Retrieving Multiple Fields

127.0.0.1:7379> HMGET product:2000 name price stock
1) "Laptop"
2) "999.99"
3) "50"

Retrieving Fields with Missing Values

127.0.0.1:7379> HMGET product:2000 name description
1) "Laptop"
2) (nil)

Invalid Usage

Trying to retrieve fields from a key that is not a hash.

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

Missing Key or Field Arguments

127.0.0.1:7379> HMGET
(error) ERR wrong number of arguments for 'hmget' command

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

Best Practices

• Use HMGET to fetch only the fields you need from a hash to minimize data transfer and improve performance.