RPUSH

Introduction and Use Case(s)

The RPUSH command in Redis is used to add one or multiple elements to the tail (right) of a list. This command is useful for maintaining queues, logs, or any ordered data structure where new items need to be added to the end.

Syntax

  1. RPUSH key element [element ...]

Parameter Explanations

  • key: The name of the list to which you want to add elements. If the list does not exist, a new list will be created.
  • element: One or more elements to be added to the list. These can be strings or other types that can be converted to a string representation.

Return Values

The RPUSH command returns an integer representing the length of the list after the push operation.

Example Outputs:

  • Adding a single element to an empty list:

    1. dragonfly> RPUSH mylist "hello"
    2. (integer) 1

  • Adding multiple elements:

    1. dragonfly> RPUSH mylist "world" "!"
    2. (integer) 3

Code Examples

  1. dragonfly> RPUSH mylist "one"
  2. (integer) 1
  3. dragonfly> RPUSH mylist "two"
  4. (integer) 2
  5. dragonfly> RPUSH mylist "three" "four"
  6. (integer) 4
  7. dragonfly> LRANGE mylist 0 -1
  8. 1) "one"
  9. 2) "two"
  10. 3) "three"
  11. 4) "four"

Best Practices

  • Ensure the list key exists and is of type list before using RPUSH. Using RPUSH on a key holding a non-list value will result in an error.
  • When adding multiple elements at once, include all elements in a single RPUSH command to optimize performance.

Common Mistakes

  • Attempting to use RPUSH on a key that holds a non-list value results in a type error.
  • Not checking the list length after multiple operations could lead to unexpected results if your application logic depends on specific list sizes.

FAQs

What happens if the list does not exist?

If the specified key does not exist, RPUSH will create a new list with the provided elements.

Can I use RPUSH with non-string values?

Yes, as long as the values can be coerced into a string format, RPUSH will accept them.

Is there a limit to the number of elements I can add with RPUSH?

Practically, the number is limited by the available memory on the Redis server. There is no explicit limit set by Redis for the number of elements per RPUSH command.