Redis is not a plain key-value store, it is actually a data structures server, supporting different kinds of values.
** 翻译：redis不是单纯的键值对存储，它实际上是个数据结构服务器，它支持各种类型的值。**
redis支持以下数据结构:
- Binary-safe strings.
- 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 (for example you may ask: give me the top 10, or the bottom 10).
- Hashes, which are maps composed of fields associated with values. Both the field and the value are strings. This is very similar to Ruby or Python hashes.
- Bit arrays (or simply 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. Don't be scared, it is simpler than it seems... See later in the HyperLogLog section of this tutorial.
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.
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.
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.
Hashes are maps between string fields and string values, so they are the perfect data type to represent objects