Command: MAP.CSET

Overview

The MAP.CSET command is used to create or overwrite a map at a specified key with a single key-value entry. If the key already exists, the previous map is completely replaced with the new one containing just the given mapKey and value .

This command is useful in situations where you want to ensure that a key holds a map with only one specific entry, replacing any old map that was present under that key.

Command Name

MAP.CSET

Description

Sets or updates a key-value pair inside a map stored at the specified key.

⚠️ Important: This command overwrites any existing map at the specified key. The new map will contain only the provided mapKey and value .

Use Cases

  • Replacing an existing device record with a new one.

  • Initializing a key with a map containing a single entry.

  • Resetting a user’s map data with a new object.

Syntax 

  MAP.CSET <key> <mapKey> <value>

  • <key> : The top-level key to store the map under.

  • <mapKey> : The key inside the map.

  • <value> : A valid JSON string representing the value for mapKey .

Permissions

  • The user must have write permissions on the given key.

  • No special roles required beyond standard modification rights.

Examples

Example 1: Add a new map with one entry 
  localhost:9219> MAP.CSET user-001:devices device-6d6f6sa66d '{
  "deviceName": "Pixel 7 Pro",
  "osVersion": "Android 14",
  "batteryLevel": "85%"
}'
Ok

localhost:9219> MAP.GET user-001:devices
Ok {
  "deviceName": "Pixel 7 Pro",
  "osVersion": "Android 14",
  "batteryLevel": "85%"
}
Example 2: Overwrite map with a new entry 
  localhost:9219> MAP.CSET user-001:devices device-663abc5352 '{
  "deviceName": "iPhone 14 Pro",
  "osVersion": "iOS 16",
  "batteryLevel": "75%"
}'

localhost:9219> MAP.GET user-001:devices
Ok {
  "deviceName": "iPhone 14 Pro",
  "osVersion": "iOS 16",
  "batteryLevel": "75%"
}

Note: After the second call, the previous "device-6d6f6sa66d" entry is removed. Only the new entry remains.

Behavior on Error

Error Condition Message Example
Missing arguments ERR: InvalidArgsError: Key mapKey, and value must be provided
Invalid key format ERR: InvalidKeyError: <details>
Invalid mapKey (empty/invalid string) ERR: InvalidMapKeyError: <details>
Internal failure during map storage ERR: <internal error message>

Internals (for developers)

  • The old map stored at <key> is deleted.

  • A new map object is created with {<mapKey>: <value>}