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DiceDB

HDEL

HDEL

The HDEL command in DiceDB deletes a specified field within a hash stored at a given key. If either the key or field does not exist, no action is taken, and 0 is returned.

Syntax

Terminal window
HDEL key field [field ...]

Parameters

ParameterDescriptionTypeRequired
keyThe key of the hash from which the field(s) are to be deleted.StringYes
fieldOne or more fields within the hash to be deleted.StringYes

Return Values

ConditionReturn Value
Field(s) deleted successfullyInteger (Number of fields deleted)
Field does not exist0
Key does not exist0
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 'hdel' command

Behaviour

When the HDEL 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 for the specified field(s) within the hash.
  • If the specified field(s) exist, they are deleted, and DiceDB returns the count of deleted fields.
  • If the key does not exist or the field(s) are not present, it returns 0.

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

Example Usage

Deleting a field from a hash

Terminal window
127.0.0.1:7379> HSET user:1000 name "John Doe"
(integer) 1
127.0.0.1:7379> HDEL user:1000 name
(integer) 1
127.0.0.1:7379> HGET user:1000 name
(nil)

Deleting multiple fields from a hash

Terminal window
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> HDEL user:1000 name age
(integer) 2

Field does not exist

Terminal window
127.0.0.1:7379> HDEL user:1000 email
(integer) 0

Key does not exist

Terminal window
127.0.0.1:7379> HDEL user:2000 name
(integer) 0

Key is not a hash

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

Attempting to delete a field in a key that is not a hash

Terminal window
127.0.0.1:7379> SET user:5000 "This is a string"
OK
127.0.0.1:7379> HDEL user:5000 name
(error) WRONGTYPE Operation against a key holding the wrong kind of value
  • Behavior: The SET command sets the key user:5000 to a string value.
  • Error: The HDEL command raises a WRONGTYPE error because user:5000 is not a hash, and HDEL only operates on hash data structures.

Wrong Number of Arguments

Terminal window
127.0.0.1:7379> HDEL
(error) ERR wrong number of arguments for 'hdel' command


127.0.0.1:7379> HDEL user:5000
(error) ERR wrong number of arguments for 'hdel' command
  • Behavior: The HDEL command requires at least two arguments: the key and the field name.
  • Error: The command fails because HDEL requires at least a key and one field as arguments. If these are not provided, DiceDB raises an error indicating an incorrect number of arguments.

Notes

  • The HDEL command is essential for managing hash data in DiceDB, allowing fields to be efficiently removed when no longer needed.