redis学习

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redis

1.redis的incr命令

    SET connections 10
    INCR connections => 11
    INCR connections => 12
    DEL connections
    INCR connections => 1

当多个客户去操作connections时，由于INCR命令是原子操作，所以会保持数据的一致性。

2.redis的存储失效设置

Redis can be told that a key should only exist for a certain length of time. This is accomplished with the EXPIRE and TTL commands.


    SET resource:lock "Redis Demo"
    EXPIRE resource:lock 120
This causes the key resource:lock to be deleted in 120 seconds. You can test how long a key will exist with the TTL command. It returns the number of seconds until it will be deleted.


    TTL resource:lock => 113
    // after 113s
    TTL resource:lock => -2
The -2 for the TTL of the key means that the key does not exist (anymore). A -1 for the TTL of the key means that it will never expire. Note that if you SET a key, its TTL will be reset.


    SET resource:lock "Redis Demo 1"
    EXPIRE resource:lock 120
    TTL resource:lock => 119
    SET resource:lock "Redis Demo 2"
    TTL resource:lock => -1

3.redis复杂结构的存储

Redis also supports several more complex data structures. The first one we'll look at is a list. A list is a series of ordered values. Some of the important commands for interacting with lists are RPUSH, LPUSH, LLEN, LRANGE, LPOP, and RPOP. You can immediately begin working with a key as a list, as long as it doesn't already exist as a different type.

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. It takes the index of the first element you want to retrieve as its first parameter and the index of the last element you want to retrieve as its second parameter. A value of -1 for the second parameter means to retrieve elements until the end of the list.


    LRANGE friends 0 -1 => 1) "Sam", 2) "Alice", 3) "Bob"
    LRANGE friends 0 1 => 1) "Sam", 2) "Alice"
    LRANGE friends 1 2 => 1) "Alice", 2) "Bob"

4.redis的set

The next data structure that we'll look at is a set. A set is similar to a list, except it does not have a specific order and each element may only appear once. Some of the important commands in working with sets are SADD, SREM, SISMEMBER, SMEMBERS and SUNION.

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"

5.排序的set

Sets are a very handy data type, but as they are unsorted they don't work well for a number of problems. This is why Redis 1.2 introduced Sorted Sets.

A sorted set is similar to a regular set, but now each value has an associated score. This score is used to sort the elements in the 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"
In these examples, the scores are years of birth and the values are the names of famous hackers.


    ZRANGE hackers 2 4 => 1) "Claude Shannon", 2) "Alan Kay", 3) "Richard Stallman"

6.redis的hash

Simple strings, sets and sorted sets already get a lot done but there is one more data type Redis can handle: 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
Check the full list of Hash commands for more information.

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