RPUSH

The RPUSH command is used in DiceDB to insert one or multiple values at the tail (right end) of a list. If the list does not exist, it is created as an empty list before performing the push operations. This command is useful for maintaining a list of elements where new elements are added to the end of the list.

Syntax

RPUSH key value [value ...]

Parameters

Parameter	Description	Type	Required
key	The name of the list where values are inserted. If it does not exist, it will be created.	String	Yes
value [value...]	One or more space separated values to be inserted at the tail of the list.	String	Yes

Return Value

Condition	Return Value
Command is successful	Integer - length of the list after execution
Syntax or specified constraints are invalid	error

Behaviour

• When the RPUSH command is executed, the specified values are inserted at the tail of the list identified by the given key.
• If the key does not exist, a new list is created and the values are inserted.
• If the key exists but is not a list, an error is returned.
• The RPUSH operation is atomic. If multiple clients issue RPUSH commands concurrently, DiceDB ensures that the list remains consistent and the values are appended in the order the commands were received.

Errors

1. Wrong Number of Arguments

   • Error Message: (error) ERR wrong number of arguments for 'rpush' command
   • Occurs if the key parameters is not provided or at least one value is not provided.

2. Wrong Type of Key or Value:

   • Error Message: (error) WRONGTYPE Operation against a key holding the wrong kind of value
   • Occurs if the key exists and is not a list. DiceDB expects the key to either be non-existent or to hold a list data type.

Example Usage

Basic Usage

Inserting a value hello into mylist

127.0.0.1:7379> RPUSH mylist "hello"
(integer) 1

Inserting Multiple Values

Inserting multiple values world, foo, bar into mylist

127.0.0.1:7379> RPUSH mylist "world" "foo" "bar"
(integer) 3

Invalid Usage: Key is Not a List

Insert the value value at the tail of the key mystring, which stores a string, not a list.

127.0.0.1:7379> SET mystring "not a list"
OK
127.0.0.1:7379> RPUSH mystring "value"
(error) WRONGTYPE Operation against a key holding the wrong kind of value

Invalid Usage: Wrong Number of Arguments

Calling RPUSH without passing any values:

RPUSH mylist
(error) ERR wrong number of arguments for 'rpush' command

Best Practices

• Check Key Type: Before using RPUSH, ensure that the key is associated with a list to avoid errors.
• Use in Conjunction with Other List Commands: The RPUSH command is often used alongside other list commands like LLEN, LPUSH, LPOP, and RPOP to manage and process lists effectively.