基本数据类型

Redis的数据类型如下：

Binary-safe strings: 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.
Lists: collections of string elements sorted according to the order of insertion. They are basically linked lists.
Sets: collections of unique, unsorted string elements.
Sorted sets: similar to Sets but where every string element is associated to a floating number value, called score. The elements are always taken sorted by their score, so unlike Sets it is possible to retrieve a range of elements
Hashes: which are maps composed of fields associated with values. Both the field and the value are strings.
Bit arrays(bitmaps): it is possible, using special commands, to handle String values like an array of bits: you can set and clear individual bits, count all the bits set to 1, find the first set or unset bit, and so forth.
HyperLogLogs: this is a probabilistic data structure which is used in order to estimate the cardinality of a set.
Streams: append-only collections of map-like entries that provide an abstract log data type.

Binary-safe string

Redis的字符串是字节序列。在Redis中字符串是二进制安全的，这意味着他们有一个已知的长度，是没有任何特殊字符终止决定的，所以可以存储任何东西，最大长度可达512兆。

> set mykey somevalue
OK
> get mykey
"somevalue"

虽然redis中value存储为字符串，但是有一些命令可以按照数字来处理，例如自增：

> set counter 100
OK
> incr counter
(integer) 101
> incr counter
(integer) 102
> incrby counter 50
(integer) 152

批量设置(atomic)：

> mset a 10 b 20 c 30
OK
> mget a b c
1) "10"
2) "20"
3) "30"

Lists

Redis Lists are implemented with linked lists because for a database system it is crucial to be able to add elements to a very long list in a very fast way. Another strong advantage, as you'll see in a moment, is that Redis Lists can be taken at constant length in constant time.

应用场景

Remember the latest updates posted by users into a social network.
Communication between processes, using a consumer-producer pattern where the producer pushes items into a list, and a consumer (usually a worker) consumes those items and executed actions. Redis has special list commands to make this use case both more reliable and efficient.

Sets

Redis Sets are unordered collections of strings. The SADD command adds new elements to a set. It's also possible to do a number of other operations against sets like testing if a given element already exists, performing the intersection, union or difference between multiple sets, and so forth.

> sadd myset 1 2 3
(integer) 3
> smembers myset
1. 3
2. 1
3. 2

应用场景

tags

Sorted sets

Hashes

Bit arrays

HyperLogLogs