Category：Database
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Time：2022-1-19
1. Spark Download https://archive.apache.org/dist/spark/ 2. Upload and decompress, configure environment variables, and configure bin directory Unzip: tar -zxvf spark-2.4.5-bin-hadoop 2 7.tgz -C /usr/local/soft/ Renamed: mv{spark-2.4.5-bin-hadoop 2 7/ spark-2.4.5 Configure environment variable: VIM / etc / profile Add environment variable: export SPARK_HOME=/usr/local/soft/spark-2.4.5export PATH=$PATH:$SPARK_HOME/bin Save configuration: source / etc / profile 3. Modify the configuration […]
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Time：2022-1-19
The original text is published on my blog: https://blog.kaciras.com/article/6/store-tree-in-database In some systems, classifying content is a necessary function. For example, e-commerce needs to classify goods to facilitate customer search; The forum will also be divided into many sections; The portal website also has to classify the content of the website. Classification is indispensable for a […]
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Time：2022-1-19
1、 Background introduction There are many split services in distributed systems. In the process of continuous iterative upgrading, the following common thorny situations will occur: For the version upgrade of a technical component, depending on the package upgrade leads to the expiration of some syntax or API, or the component fixes urgent vulnerabilities, which will […]
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Time：2022-1-19
preface After reading what elastic search is and understanding the concept of inverted index, let’s get familiar with some common nouns in ES. Common terms noun explain cluster If one or more nodes specify the same cluster name, they will form a cluster and automatically elect the master and in case of failure. node The […]
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Time：2022-1-19
1、 Node JS basic operation for mongodb 1. Database startup First of all, we should start the database and establish a folder to store the database documents. asD:\mongo, nextcmdType the command in the-> mongod –dbpath D:\mongoTo start the database. As shown in the figure below: Then keep thiscmdThe control panel is in this state to […]
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Time：2022-1-19
In order to find out the detailed rules and regulations of the company, it is necessary to provide relevant permits and regulations/ Code > if you don’t use the diaphragm guide before reading, you will be able to stop the power when the document is sent? Windows? code>emojiWin + The license can make people come […]
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Time：2022-1-19
Approaching the college entrance examination season, a QQ group robot assisting volunteer filling is made here to record the specific implementation process.The effects achieved are as follows: Allelic query College information query This article is a series of articles. For a complete reproduction, please read it in the following order: Developing QQ chat robot with […]
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Time：2022-1-18
Row lock For database tablesRow recordLock.For example, the ID is the table primary key of table1When the data with id = 1 exists, the SQL statement: update table1 set field1=param1 where id=1; (Or delete from table1 where id = 1;Or select * from table1 where id = 1 for update; )In fact, it is the […]
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Time：2022-1-18
mysql5. 7 installation process:https://www.jianshu.com/p/bf1717d9fc93 We use the most commonly used and simple scheme for small and medium-sized enterprises. We use keepalived to provide a VIP (virtual IP) to realize switching and load balancing. Under this IP, we follow two MySQL instances, realize load balancing through keepalived’s own load balancing algorithm and mode, and realize automatic […]
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Time：2022-1-18
Don’t talk much, Kailu @Select annotation: in fact, the corresponding SQL statement is added after the annotation, and the writing method is consistent with that in [email protected] annotation: there is an ID attribute, which can be understood as defining a method that can be referenced by ID. the reference method is resultmap (“”)@ Results can […]
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Time：2022-1-18
Before opening, say a digression. The difference between multi data source and dynamic data source. Multiple data sources are generally used to connect multiple business independent databases (possibly heterogeneous databases). Dynamic data source is generally used for data segmentation in large applications. Configuration reference There are a lot of online tutorials on how to configure […]
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Time：2022-1-18
Introduction: Recently, through in-depth study of spring cloud gateway, we found that the architecture design of this framework is very simple and effective, and the design of many components is very worth learning. This paper makes a brief introduction to spring cloud gateway and a detailed analysis of the processing flow of a request for […]
