Command: LIST.ISET

Overview

The LIST.ISET command allows users to insert or replace an element at a specified index in a list stored at the provided key. This operation is index-based, and it does not extend the list—an out-of-range index returns an error.

Command Name

LIST.ISET

Description

Sets the value at the specified index of a list. If the key does not exist and the index is zero, a new list is created with the element. For any other index on a non-existent list, or if the index is out of range for an existing list, the command returns an error.

Use Cases

  • Replacing an element in a list at a known index.

  • Initializing a list with the first element.

  • Modifying a specific list entry based on zero-based index.

Syntax 

  LIST.ISET <key> <index> <value>

  • <key> : A valid string key under which the list is stored.

  • <index> : A zero-based index at which to set the element.

  • <value> : The new value to store at the index. Can be any valid JSON value or string.

Permissions

  • Read/Write access to the key space.

  • Valid only for authenticated users if your system enforces auth.

  • Must follow key naming and formatting rules.

Examples

Setting the first element 
  localhost:9219> LIST.ISET myKey 0 "This is my first element"
Ok

localhost:9219> LIST.GET myKey
Ok [
  "This is my first element"
]
Setting another element in the same list 
  localhost:9219> LIST.ISET myKey 1 "This is my second element"
Ok

localhost:9219> LIST.GET myKey 1
Ok "This is my second element"

Behavior on Error

Condition Error Message
No arguments InvalidKeyError: Key must be provided
Incorrect number of arguments InvalidArgsError: invalid number of arguments, Syntax: LIST.ISET <key> <index> <value>
Invalid index (non-integer or < 0) InvalidArgsError: Invalid index value. The index must be a number >= 0
Index out of range for existing list InvalidIndexError: index out of range
Index > 0 on non-existing list InvalidIndexError: index out of range