Redis Sorted Lists are a powerful data structure that associates a rank with each item in a set. While they are similar to regular sets, they use different commands and provide additional functionality.
To start using Redis Sorted Lists, you’ll need to use the ZADD command instead of SADD. When using ZADD, you provide a score along with the value:
ZADD names 1 "Flavio"
ZADD names 2 "Syd"
ZADD names 2 "Roger"
As shown in the example, the values in the list must still be unique, but they are now associated with a score. The score doesn’t have to be unique and can be used to sort the items in the set.
To retrieve the score of an item, you can use the ZRANK command:
ZRANK names "Flavio"
To list all the items in the sorted set, you can use the ZRANGE command, which is similar to LRANGE for regular lists:
ZRANGE names 0 -1
This will return all the items in the list.
If you want to retrieve the scores along with the items, you can add the WITHSCORES option:
ZRANGE names 0 -1 WITHSCORES
This will return a list of items with their respective scores.
Redis Sorted Lists also provide the ability to increment the score of an item within the set using the ZINCRBY command.
Redis provides many more commands for working with Sorted Lists, and you can find a comprehensive list here.
Overall, Redis Sorted Lists are particularly useful for implementing data storage tools such as leaderboards or tracking the time of item additions with timestamps.