Redis - key/value store

Setting server:name as key to the value of "fido"

SET server:name "fido"
GET server:name => "fido"

Increment and Delete

SET connections 10
INCR connections => 11
INCR connections => 12
DEL connections
INCR connections => 1
// SETNX - SET-if-not-exists
// INCR - is an atomic operation

Expire and Time To Live

SET resource:lock "Redis Demo"
EXPIRE resource:lock 120

TTL resource:lock => 113
// after 113s
TTL resource:lock => -2 (-2 means that the key does not exist, -1 means that the key will never expire)

SET resource:lock "Redis Demo 1"
EXPIRE resource:lock 120
TTL resource:lock => 119
SET resource:lock "Redis Demo 2" // Setting a key will reset the key's TTL
TTL resource:lock => -1

Lists

RPUSH puts the new value at the end of the list.

RPUSH friends "Alice"
RPUSH friends "Bob"

LPUSH puts the new value at the start of the list.

LPUSH friends "Sam"

LRANGE gives a subset of the list. A value of -1 for the second parameter means to retrieve elements until the end of the list.

LRANGE friends 0 -1 => ["Sam","Alice","Bob"]
LRANGE friends 0 1 => ["Sam","Alice"]
LRANGE friends 1 2 => ["Alice","Bob"]

LLEN returns the current length of the list.

LLEN friends => 3

LPOP removes the first element from the list and returns it.

LPOP friends => "Sam"

RPOP removes the last element from the list and returns it.

RPOP friends => "Bob"

Sets

SADD adds the given value to the set.

SADD superpowers "flight"
SADD superpowers "x-ray vision"
SADD superpowers "reflexes"

SREM removes the given value from the set.

SREM superpowers "reflexes"

SISMEMBER tests if the given value is in the set.

SISMEMBER superpowers "flight" => true
SISMEMBER superpowers "reflexes" => false

SMEMBERS returns a list of all the members of this set.

SMEMBERS superpowers => ["flight","x-ray vision"]

SUNION combines two or more sets and returns the list of all elements.

SADD birdpowers "pecking"
SADD birdpowers "flight"
SUNION superpowers birdpowers => ["flight","x-ray vision","pecking"]

Sorted Sets - with score

ZADD adds the given score and value to the sorted set

ZADD hackers 1940 "Alan Kay"
ZADD hackers 1906 "Grace Hopper"
ZADD hackers 1953 "Richard Stallman"
ZADD hackers 1965 "Yukihiro Matsumoto"
ZADD hackers 1916 "Claude Shannon"
``ZADD hackers 1969 "Linus Torvalds" ZADD hackers 1957 "Sophie Wilson"`
`ZADD hackers 1912 "Alan Turing"`

ZRANGE gives a subset of the sorted set

ZRANGE hackers 2 4 => ["Claude Shannon", "Alan Kay","Richard Stallman"]

Hashes

Hashes are maps between string fields and string values, so they are the perfect data type to represent objects (eg: A User with a number of fields like name, surname, age, and so forth):

HSET user:1000 name "John Smith"
HSET user:1000 email "john.smith@example.com"
HSET user:1000 password "s3cret"

To get back the saved data use HGETALL:

HGETALL user:1000

You can also set multiple fields at once:

HMSET user:1001 name "Mary Jones" password "hidden" email "mjones@example.com"

If you only need a single field value that is possible as well:

HGET user:1001 name => "Mary Jones"

Numerical values in hash fields are handled exactly the same as in simple strings and there are operations to increment this value in an atomic way.

HSET user:1000 visits 10
HINCRBY user:1000 visits 1 => 11
HINCRBY user:1000 visits 10 => 21
HDEL user:1000 visits
HINCRBY user:1000 visits 1 => 1