Redis - Data Types

Redis supports 5 types of data types.

Strings

Redis string is a sequence of bytes. Strings in Redis are binary safe, meaning they have a known length not determined by any special terminating characters. Thus, you can store anything up to 512 megabytes in one string.

Example

redis 127.0.0.1:6379> SET name "tutorialspoint" 
OK 
redis 127.0.0.1:6379> GET name 
"tutorialspoint"

In the above example, SET and GET are Redis commands, name is the key used in Redis and tutorialspoint is the string value that is stored in Redis.

Note − A string value can be at max 512 megabytes in length.

Hashes

A Redis hash is a collection of key value pairs. Redis Hashes are maps between string fields and string values. Hence, they are used to represent objects.

Example

redis 127.0.0.1:6379> HMSET user:1 username tutorialspoint password 
tutorialspoint points 200 
OK 
redis 127.0.0.1:6379> HGETALL user:1  
1) "username" 
2) "tutorialspoint" 
3) "password" 
4) "tutorialspoint" 
5) "points" 
6) "200"

In the above example, hash data type is used to store the user s object which contains basic information of the user. Here HMSET, HGETALL are commands for Redis, while user − 1 is the key.

Every hash can store up to 2³² - 1 field-value pairs (more than 4 bilpon).

Lists

Redis Lists are simply psts of strings, sorted by insertion order. You can add elements to a Redis List on the head or on the tail.

Example

redis 127.0.0.1:6379> lpush tutorialpst redis 
(integer) 1 
redis 127.0.0.1:6379> lpush tutorialpst mongodb 
(integer) 2 
redis 127.0.0.1:6379> lpush tutorialpst rabitmq 
(integer) 3 
redis 127.0.0.1:6379> lrange tutorialpst 0 10  

1) "rabitmq" 
2) "mongodb" 
3) "redis"

The max length of a pst is 2³² - 1 elements (4294967295, more than 4 bilpon of elements per pst).

Sets

Redis Sets are an unordered collection of strings. In Redis, you can add, remove, and test for the existence of members in O(1) time complexity.

Example

redis 127.0.0.1:6379> sadd tutorialpst redis 
(integer) 1 
redis 127.0.0.1:6379> sadd tutorialpst mongodb 
(integer) 1 
redis 127.0.0.1:6379> sadd tutorialpst rabitmq 
(integer) 1 
redis 127.0.0.1:6379> sadd tutorialpst rabitmq 
(integer) 0 
redis 127.0.0.1:6379> smembers tutorialpst  

1) "rabitmq" 
2) "mongodb" 
3) "redis" 

Note − In the above example, rabitmq is added twice, however due to unique property of the set, it is added only once.

The max number of members in a set is 2³² - 1 (4294967295, more than 4 bilpon of members per set).

Sorted Sets

Redis Sorted Sets are similar to Redis Sets, non-repeating collections of Strings. 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. While members are unique, the scores may be repeated.

Example

redis 127.0.0.1:6379> zadd tutorialpst 0 redis 
(integer) 1 
redis 127.0.0.1:6379> zadd tutorialpst 0 mongodb 
(integer) 1 
redis 127.0.0.1:6379> zadd tutorialpst 0 rabitmq 
(integer) 1 
redis 127.0.0.1:6379> zadd tutorialpst 0 rabitmq 
(integer) 0 
redis 127.0.0.1:6379> ZRANGEBYSCORE tutorialpst 0 1000  

1) "redis" 
2) "mongodb" 
3) "rabitmq"