REDIS: NOSQL DATA STORAGE

Transcription

1 REDIS: NOSQL DATA STORAGE 1 Presented By- Shalini Somani (13MCEC22)

2 CATEGORIES OF NOSQL STORAGES Key-Value memcached Redis Column Family Cassandra HBase Document MongoDB Tabular BigTable Graph, XML, Object, Multivalued, 2

3 REDIS Redis is an open source, advanced key-value data store. Often referred to as a data structure engine - Strings - Hashes - Sets - Lists - Ordered Sets 3

4 REDIS ARCHITECTURE 4

5 REDIS Regardless of the type, a value is accessed by a key. It is possible to persist dataset either by dumping the dataset to disk every once in a while. or by appending each command to a log. 5

6 WHO IS USING REDIS? 6

7 INSTALLATION Linux: Windows 1. Clone from Git repo: 2. Unzip file from /redis/bin/release (e.g. redisbin64.zip) to /redis 3. Important files: /redis/redis-server.exe /redis/redis-cli.exe 7

8 CONFIGURATION Configuration file: /redis/redis.conf It is possible to change a port (if you wish): port 6379 For development environment it is useful to change data persisting policy save save save save 10 1 save after 10 sec if at least 1 key changed 8

9 RUNNING REDIS SERVER Run /redis/bin/redis-server.exe and specify configuration file to use redis>redis-server redis.conf 9

10 RUNNING REDIS CLIENT Run /redis/bin/redis-cli.exe Now you can play with Redis a little bit 10

11 USEFUL COMMANDS Print all keys: KEYS * Remove all keys from all databases FLUSHALL Synchronously save the dataset to disk SAVE 11

12 REDIS KEYS Keys are binary safe - it is possible to use any binary sequence as a key The empty string is also a valid key Too long keys are not a good idea Too short keys are often also not a good idea ("u:1000:pwd" versus "user:1000:password") Nice idea is to use some kind of schema, like: "object-type:id:field" 12

13 BASIC COMMANDS DBSIZE - returns the number of keys in the database. % DBSIZE :0 This is a new database with no keys, so Redis says :0. NOTE:- at a time Redis supports 16 Databases (0-15). (this is the default no of databases which can me manually changed in redis.cofig file) We can navigate between various databases using- SELECT [database_no] 13

14 BASIC COMMANDS GET - fetches the value at the provided key. % GET hello $ -1 The key hello doesn t exist, so Redis says $- 1,which is like nil or null. Let s set a value for that key: 14

15 BASIC COMMANDS SET - it is used to set the value of a key. syntax- SET [key] [value] example- % SET hello nirma +OK Here Nirma is value for key hello. 15

16 BASIC COMMANDS Here, we SET the key hello to the 5-byte value world, and Redis says +OK. Now if we GET again: % GET hello nirma EXIST- to check if a key exist. % EXISTS mykey :0 % EXISTS hello :1 16

17 BASIC COMMANDS SETNX if we want to set value of key if it doesn t exist. % SETNX elective % I have opted for MD. :1 % GET elective I have opted for MD. % SETNX elective % Artificial Intelligence :0 % GET elective I have opted for MD. The second SETNX fails because the key elective, having been created by the first SETNX, now exists. 17

18 INCREMENT & DECREMENT Redis lets us increment and decrement our values. First, let s create a counter and set it to 1: % SET counter 1 % 1 +OK To increment: % INCR counter :2 To decrement: % DECR counter :1 We can also increment and decrement by values other than one: % INCRBY counter 5 :6 % DECRBY counter 6 :0 18

19 WHY INCREMENT AND DECREMENT COMMANDS EXIST? Example- we re using Redis to track the pageviews for a web site. Every URL maps to a key whose value is a counter. When a user visits a URL, we increment the counter. Imagine two visitors, v1 and v2, visit the same URL,about, at the same time. The Redis code for this might be- 19

20 WHY INCREMENT AND DECREMENT COMMANDS EXIST? redis.get("/about") == 5 v1 = redis.get("/about") v2 = redis.get("/about") # 5 visits so far # visitor 1 grabs the count # visitor 2 grabs the count redis.set("/about", v1 + 1) # visitor 1 sets the count + 1 redis.set("/about", v2 + 1) # visitor 2 sets the count + 1 redis.get("/about") == 6 # what?? should be 7 Solution-: The increment and decrement commands prevent this problem because they re atomic: reading the value and changing it occur in one motion and can t be interrupted. 20

21 REDIS DATA TYPES Redis is often referred to as a data structure server since keys can contain: Strings Lists Sets Hashes Sorted Sets 21

22 REDIS STRINGS Most basic kind of Redis value. Binary safe - can contain any kind of data, for instance a JPEG image or a serialized Ruby object. Max 512 Megabytes in length. Can be used as atomic counters using commands in the INCR family. Can be appended with the APPEND command. 22

23 REDIS STRINGS: EXAMPLE 23

24 REDIS LISTS Lists of strings, sorted by insertion order. Lists let you associate an array of values to a single key. Max length: (2^32-1) elements. Model a timeline in a social network, using LPUSH to add new elements, and using LRANGE in order to retrieve recent items. Use LPUSH together with LTRIM to create a list that never exceeds a given number of elements 24

25 REDIS LISTS: EXAMPLE 25

26 SETS Sets are a lot like lists, except they provide set-semantics (no duplicate values in a given set). Various SET operations-: 1. SADD- Add one or more members to a SET. 2. SCARD- Get the number of memners in a SET. 3. SDIFF- Subtract multiple SETS. 4. SISMEMBER- Determine if a given value is member of SET. 5. SINTER- Intersect multiple SETS. 6. SMEMBERS- Display all members of a SET...etc. 26

27 SET EXAMPLE 27

28 REDIS SORTED SETS Every member of a Sorted Set is associated with score, that is used in order to take the sorted set ordered, from the smallest to the greatest score. A sorted set is similar to a set, except each value is associated (and sorted by) a score field. In other words, when you add a value to a sorted set, you also specify the score as a number. This determines the order of the value within the set. Probably the most advanced Redis data type 28

29 ORDERED SET EXAMPLE 29

30 REDIS HASHES Map between string fields and string values. Perfect data type to represent objects. Rather than manipulating a key directly (like with a String) you manipulate the fields of a key. 30

31 HASH EXAMPLE 31

32 REDIS OPERATIONS It is possible to run atomic operations on data types: appending to a string incrementing the value in a hash pushing to a list computing set intersection, union and difference getting the member with highest ranking in a sorted set 32

33 USING REDIS IN JAVA JRedis - Java Client for Redis Jedis - a blazingly small and sane Redis Java client Spring Data Redis 33

34 SPRING DATA PROJECT Provides integration and support for many types of databases Big Data: Apache Hadoop Key-Value: Redis Document: MongoDB Graph: Neo4j Column: HBase 34

35 REDIS COMMANDS. 35

36 36

37 37

38 38

39 39

40 40

41 41

42 RESOURCES Redis 42