Introduction to NoSQL database

NoSQL Database introduction

 The classification of Technology ：
1、 Solve functional problems ：Java、Jsp、RDBMS、Tomcat、HTML、Linux、JDBC、SVN
2、 Solve the problem of scalability ：Struts、Spring、SpringMVC、Hibernate、Mybatis
3、 Solve performance problems ：NoSQL、Java Threads 、Hadoop、Nginx、MQ、ElasticSearch

1、Web1.0 Time

Web1.0 Era , Data access is limited , Most problems can be solved by using a single point server with high performance .

2、Web2.0 Time

With Web2.0 The coming of the era of , The number of user visits has increased significantly , At the same time, a large amount of user data is generated . Coupled with the popularity of smart mobile devices later , All Internet platforms face huge performance challenges .

3、 solve CPU And memory pressure

4、 solve IO pressure

NoSQL database

NoSQL Database Overview

NoSQL(NoSQL = Not Only SQL ), meaning “ not only SQL”, A general term for a non-relational database .

NoSQL It doesn't rely on business logic to store , In a simple way key-value Mode storage . Therefore, the expansion ability of the database is greatly increased .

• Non compliance SQL standard .
• I won't support it ACID.
• Far beyond SQL Performance of .

NoSQL Applicable scenario

• High concurrent reading and writing of data
• Read and write massive data
• High scalability of data

NoSQL Not applicable to the scene

• Need transaction support .
• be based on sql Structured query storage of , Dealing with complex relationships , You need to make an ad hoc inquiry .
• （ Not need sql And used sql It doesn't work , Please consider using NoSql）

Memcache

• It's very early NoSql database
• The data is in memory , Generally not persistent
• Support simple key-value Pattern , Support single type
• Generally, it is used as a cache database to assist persistence

Redis

• It's almost covered Memcached Most functions of
• The data is in memory , Support persistence , Mainly used for backup and recovery
• In addition to supporting simple key-value Pattern , It also supports the storage of multiple data structures , such as list、set、hash、zset etc. .
• Generally, it is used as a cache database to assist persistence

MongoDB

• High performance 、 Open source 、 Model freedom (schema free) Document database of
• The data is in memory , If there is not enough memory , Save infrequently used data to hard disk
• Although it is key-value Pattern , But yes. value（ In especial json） Provides rich query functions
• Support binary data and large objects
• It can be replaced according to the characteristics of the data RDBMS , Become an independent database . Or cooperation RDBMS, Store specific data .

Line storage database （ Big data era ）

1、 Row database

2、 Columnar database

Hbase

HBase yes Hadoop The database in the project . It's used for the need to randomize large amounts of data 、 In the scene of real-time read-write operation .
HBase Our goal is to deal with tables with a huge amount of data , It can be processed by ordinary computer 10 Billion lines of data , It can also handle data tables with millions of columns of elements .

Cassandra[kəˈsændrə]

Apache Cassandra It's a free open source NoSQL database , It is designed to manage massive datasets on a large cluster built by a large number of commercial servers ( The amount of data usually reaches PB Level ). Among the many remarkable features ,Cassandra The most outstanding advantage is the scaling of write and read operations , Moreover, it does not emphasize the design idea of the main cluster, which can simplify the creation and expansion process of each cluster in a relatively intuitive way .

 Computer storage unit   Computer storage units are generally used B,KB,MB,GB,TB,EB,ZB,YB,BB To express , The relationship between them is ：
 position  bit ( The bit )(Binary Digits)： A binary number holds one bit , namely  0  or  1, The smallest unit of storage .
 byte  byte：8 A binary bit is a byte (B), The most commonly used unit .
1KB (Kilobyte  kilobytes )=1024B,
1MB (Megabyte  Megabytes   abbreviation “ mega ”)=1024KB,
1GB (Gigabyte  Gigabyte   also called “ Gigabit ”)=1024MB,
1TB (Trillionbyte  Trillion bytes   Terabytes )=1024GB, among 1024=2^10 ( 2  Of 10 Power ),
1PB（Petabyte  Billions of bytes   Petabyte ）=1024TB,
1EB（Exabyte  10 billion bytes   Ebyte ）=1024PB,
1ZB (Zettabyte  One trillion bytes   Zebyte )= 1024 EB,
1YB (Jottabyte  100 billion bytes   Yao byte )= 1024 ZB,
1BB (Brontobyte  100 billion bytes )= 1024 YB.
 notes ：“ mega ” In millions of orders of magnitude .

Graph relational database

Main application ： Social relations , Public transport network , Map and network topology (n*(n-1)/2)

DB-Engines Database ranking

http://db-engines.com/en/ranking