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I would like to know how to store a list of objects in Redis. That is I have a key like this.
users:pro
{
name: "Bruce", age: "20", score: 100,
name: "Ed", age: "22", score: 80
}
Where I will want to store a list of hashes as value of a particular key. I would like to use the score field as the score field in the sorted set. How could I accomplish this?
I have seen writing a putting a single hash for a key, but what if I want multiple hashes and one of the hash fields must act as a score field for the sorted set?
291
In Redis, sorted sets are a data type similar to sets in that both are non repeating groups of strings. The difference is that each member of a sorted set is associated with a score, allowing them to be sorted from the smallest score to the largest.
Sorting in Redis is similar to sorting in other languages: we want to take a sequence of items and order them according to some comparison between elements. SORT allows us to sort LIST s, SET s, and ZSET s according to data in the LIST / SET / ZSET data stored in STRING keys, or even data stored in HASH es.
Redis and PHP Redis Sorted Sets are similar to Redis Sets with the unique feature of values stored in a set. The difference is, every member of a Sorted Set is associated with a score, that is used in order to take the sorted set ordered, from the smallest to the greatest score.
A Redis sorted set is a collection of unique strings (members) ordered by an associated score. When more than one string has the same score, the strings are ordered lexicographically. Some use cases for sorted sets include: Leaderboards.
Using a single key to store all your hashes will require some serialization as Redis doesn't support nested data structures. The result would be the following:
key: users:pro
|
+-----> field value
name:Bruce "age: 20, score: 100"
name:Ed "age: 22, score: 80"
> HMSET users:pro name:Bruce "age: 20, score: 100" name:Ed "age:22, score:80"
The corresponding Sorted Set would be:
key: users:pro.by_scores
|
+---> scores: 80 100
+---> values: "name:Ed" "name:Bruce"
> ZADD users:pro.by_scores 80 "name:Ed" 100 "name:Bruce"
Note 1: this approach mandates a unique ID per-user, currently the name property is used which could be problematic.
Note 2: to avoid the serialization (and deserialization), you can consider using a dedicated key per user. That means doing:
key: users:pro:Bruce
|
+-----> field value
age 20
score 100
key: users:pro:Ed
|
+-----> field value
age 22
score 80
> HMSET users:pro:Bruce age 20 score 100
> HMSET users:pro:Ed age 22 score 80
key: users:pro.by_scores
|
+---> scores: 80 100
+---> values: "users:pro:Ed" "users:pro:Bruce"
> ZADD users:pro.by_scores 80 "users:pro:Ed" 100 "users:pro:Bruce"
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