redis: nosql data storage · redis regardless of the type, a value is accessed by a key. it is...
TRANSCRIPT
REDIS: NOSQL DATA
STORAGE
Presented By-
Shalini Somani
(13MCEC22)
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CATEGORIES OF NOSQL STORAGES
Key-Value
memcached
Redis
Column Family
Cassandra
HBase
Document
MongoDB
Tabular
BigTable
Graph, XML, Object, Multivalued,…
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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
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REDIS ARCHITECTURE
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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.
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WHO IS USING REDIS?
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INSTALLATION
Linux: http://redis.io/download
Windows
1. Clone from Git repo: https://github.com/MSOpenTech/redis
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
CONFIGURATION
Configuration file: /redis/redis.conf
It is possible to change a port (if you wish):
For development environment it is useful to change data persisting policy
port 6379
save 900 1
save 300 10
save 60 10000
save 10 1
save after 10 sec if at least 1 key changed
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RUNNING REDIS SERVER
Run /redis/bin/redis-server.exe and specify configuration file to use
redis>redis-server redis.conf
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RUNNING REDIS CLIENT
Run /redis/bin/redis-cli.exe
Now you can play with Redis a little bit
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USEFUL COMMANDS
Print all keys:
Remove all keys from all databases
Synchronously save the dataset to disk
KEYS *
FLUSHALL
SAVE 11
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"
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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
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:
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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
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
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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.
The second SETNX fails because the key ”elective”, having been created by
the first SETNX, now exists.
% SETNX elective
% Artificial
Intelligence
:0
% GET elective
I have opted for MD.
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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
We can also increment and decrement by values other than one:
To increment:
% INCR
counter :2
To decrement:
% DECR
counter :1
% INCRBY counter 5
:6
% DECRBY counter 6
:0 18
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-
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WHY INCREMENT AND DECREMENT
COMMANDS EXIST?
redis.get("/about") == 5 # 5 visits so far
v1 = redis.get("/about") # visitor 1 grabs the count
v2 = redis.get("/about") # 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.
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REDIS DATA TYPES
Redis is often referred to as a data structure server since keys can contain:
Strings
Lists
Sets
Hashes
Sorted Sets
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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.
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REDIS STRINGS: EXAMPLE
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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
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REDIS LISTS: EXAMPLE
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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.
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SET EXAMPLE…
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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
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ORDERED SET EXAMPLE
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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.
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HASH EXAMPLE
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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
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USING REDIS IN JAVA
JRedis - Java Client for Redis
Jedis - a blazingly small and sane Redis Java client
Spring Data Redis
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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
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REDIS COMMANDS….
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