• MySQL concurrent processing


    Concurrent processing When multiple connections modify records, ensure data consistency and integrity Why use concurrency control Suppose there are commodity records in our database, and now there are two users logging in. Suppose a user wants to delete a record with ID 22 and a user wants to read a record with ID 22, what […]

  • MySQL restores data through binlog


    objective By understanding the relevant configuration of binlog log, you can simply master the data recovery operation of database through binlog; MySQL log file Any mature software will have a mature log system. When there is a problem with the software, these logs are the treasure house to query the source of the problem. Similarly, […]

  • Comparison of common technologies and schemes of database recovery subsystem (I)


    Author: Xiao Chen / big data open laboratory For transactional database, the key function is to ensure the acid attribute of things, in which atomicity and persistence depend on the recovery subsystem. If it is found that the transaction cannot continue during the transaction, it needs to be rolled back with the recovery subsystem; Or […]

  • Comparison of common technologies and schemes of database recovery subsystem (2)


    Author: Xiao Chen / big data open laboratory Last article《Comparison of common technologies and schemes of database recovery subsystem (I)》In, we basically introduce the logging & recovery recovery subsystem in the database management system, and discuss in detail the concept and technical implementation of Aries, the mainstream recovery algorithm based on physical logging. This article […]

  • [Mr. Zhao Qiang] redis case analysis: using setbit to count active users


    1、 Demand background First, let’s take a look at the requirements: the website counts the number of user logins, as follows: The website has 100 million users, including those who log in frequently and those who log in infrequently How to record user login information How to query active users: for example, log in three […]

  • Mybatis extension — General mapper and dynamic resultmap


    preface The JPA used by the company in the past is very convenient. For new projects, I choose to use mybatis. SQL is written in XML files. Although the basic methods are generated by tools, once a field is added to the data, it is really uncomfortable to modify these methods. Moreover, I feel really […]

  • Leetcode 1109 flight reservation statistics


    subject here you are   n   Flights, numbered from 1 to n. There is a flight reservation form   Bookings, table No   i   Reservation records   bookings[i] = [firsti, lasti, seatsi]   Means from firstI   Seatsi is booked on each flight to lasti (including firstI and lasti)   Seats. Please return […]

  • 🍖 Transaction isolation mechanism


    1、 Introduction to transaction isolation mechanism Transaction hasAtomicity, consistency, isolation, persistenceFour characteristics andIsolationAs the name suggests, transactions are isolated from each other. When multiple transactions process a data at the same time, they do not affect each other. If the isolation is not good enough, there may be problemsDirty reading, unrepeatable reading, phantom reading, etcphenomenon […]

  • Mongodb basic operation


    More welcome to the blog:https://imjianjian.github.io Mongodb version: 3.4 consult your documentation find() Query all db.collection.find({}) db.collection.find() Document query //Query all documents with name = “Jian” db.collection.find({“collection”:”jianjian”}) Conditional Operator $LT less than $GT greater than $GTE is greater than or equal to $LTE less than or equal to $ne is not equal to $all inclusive $in […]

  • PostgreSQL slow query statement record and analysis


    1. Record PostgreSQL takes version 12 as an example We need to open the slow query log of PostgreSQL first. This is a precondition. First record our queries for a long time. Edit profile:/var/postgres12/data/postgresql.conf #log_min_duration_statement = -1 # -1 is disabled, 0 logs all statements # and their durations, > 0 logs only # statements […]

  • Elementui implements table row dragging based on Vue + sortable.js


    Table row dragging based on Vue + sortable.js By: guest granting QQ: 1033553122 Practice environment [email protected] [email protected] [email protected] Install sortable.js drag and drop Library npm install sortablejs Code example import Sortable from “sortablejs”; export default { data() { return { tableData: [ { date: “2016-05-02”, Name: “Wang Xiaohu 1”, Address: “1, Lane 1518, Jinshajiang Road, […]

  • [Part 8] – git view the B2B2C e-commerce technology summary of spring cloud live mall submitting history


    Git view submission historyGit submission history generally uses two commands: git logAfter submitting several updates using git, or cloning a project, we can use git to review the submission history   git log   Command view. For the operations in our previous chapter, use   git log   The command lists the commit history as […]