JAVA combat articles Simple application of the transaction manager that comes with Spring Programmatic transaction Declarative transaction, annotation declarative transaction, AspectJ annotation transaction

The transaction manager that comes with Spring 1. Programmatic transactions For details, please refer to the official documentation: https://www.docs4dev.com/docs/zh/spring-framework/5.1.3.RELEASE/reference/data-access.html#transaction-programmatic Advantages: no need for spring to proxy, generate proxy objects (reflection), better performanc ...

Posted by irkevin on Sat, 30 Apr 2022 15:40:21 +0300

Naming Specification for MySQL

1. Naming Specification 1.1 Specification for Library Construction Databases, tables, fields, indexes are all lowercase letters, and English words are underlined () Separate. 1.2 Table Field Specification The column design specification uses tinyint/int/bigint according to business area, which takes up 1/4/8 bytes, respectively. Use tinyint ...

Posted by Bramme on Sat, 30 Apr 2022 03:48:57 +0300

Record local installation oushudb - install zk and hdfs

Because the company is busy recently, I forgot to update it. Then I talked about it in the last article, The last article said This article describes some preparations for installing oushudb. This article mainly talks about the installation of corresponding components before installing oushudb. 1, Zookeper installation 1. Create a zkhostfile c ...

Posted by Chips on Sat, 30 Apr 2022 00:19:07 +0300

14_ Users and permissions

theory 1. User column The user column of the user table includes Host, user and password, which represent Host name, user name and password respectively. Where user and Host are the joint primary nodes of the user table. When establishing a connection between the user and the server, the user name, Host name and password in the entered ac ...

Posted by apulmca on Fri, 29 Apr 2022 09:42:09 +0300

Performance comparison test of random forest algorithm implementation: scikit-learn, Spark MLlib, DolphinDB, xgboost

Random forests are commonly used machine learning algorithms that can be used for both classification and regression problems. This article compares and tests the implementation of random forest algorithm on four platforms, scikit-learn, Spark MLlib, DolphinDB, and xgboost. Evaluation metrics include memory footprint, running speed, and classif ...

Posted by djroki on Fri, 29 Apr 2022 09:01:44 +0300

1. Introduction to FlashTsDB time series database

  Introduction to FlashTsDB time series database 1,What is FlashTsDB 1.1 Background With the continuous development of the Internet and the Internet of Things, the storage demand for massive data with time series characteristics is increasing, and TSDB (Time Series Database) has begun to receive more attention. Traditional commercial time-s ...

Posted by thestars on Fri, 29 Apr 2022 03:29:56 +0300

Mybatis complex query (many-to-many, one-to-many, many-to-one)

We know that it is very easy to complete single-table query in Mybatis, and multi-table query is a difficult point in the Mybatis framework, which needs to be mastered. 1. Many-to-many query There is a many-to-many relationship between users and groups, and the requirement is: find all group information by user id The database design ...

Posted by nonexistentera on Fri, 29 Apr 2022 03:20:50 +0300

MySQL master-slave replication and read-write separation

1, Deployment reasons reason: Ensure that the data of the master database and the slave database are always, and prevent single point of failure and data lossIn enterprise applications, mature businesses usually have a large amount of dataA single MySQL cannot meet the actual needs in terms of security, high availability and high concurre ...

Posted by bbristow on Thu, 28 Apr 2022 20:50:46 +0300

(the most complete SQL statement, without one!) Explain SQL statement syntax in detail according to classification

catalogue 1, Foundation 1. Description: create database 2. Description: delete database 4. Description: create a new table 5. Create a new table based on the existing table: 6. Description: add a column 7. Description: add primary key: 8. Index creation Description: 9. Description: create view: 10. Several basic sql statements 11. De ...

Posted by fatherlyons on Thu, 28 Apr 2022 09:06:55 +0300

OpenSUSE installation of PostGIS 3 (Postgresql 13)

catalogue1. Get PostGIS software source2. Install PostGIS software3. Configure PostGIS software4. Start the PostGIS service 1. Get PostGIS software source Directly to https://software.opensuse.org/explor Website, select the corresponding distribution, search postgis, and then find the version to be installed in the search results to view releva ...

Posted by tomsasse on Thu, 28 Apr 2022 03:46:16 +0300