• Things you don’t know about Kafka and rocketmq underlying storage


    Hello, I’m yes. We all know that rocketmq and Kafka messages are stored on the disk. Why can the messages be read and written on the disk so fast? Have you done any optimization? They are both memory disks. What is the difference between their implementation? What are the advantages and disadvantages of each? Today […]

  • Do you really know the load method?


    Pay attention to the warehouse and get updated in time: IOS source code analyzeFollow: Draveness · Github Because the runtime of objc can only be compiled under Mac OS, the code in this article is in Mac OS, that is to sayx86_64Architecture, for the code running in arm64 will be specially described. Write it at […]

  • Full record of. Net core microservices Introduction (6) — eventbus event bus


    Tips: This article has been added to the reading list of series articles. You can click to see more related articles. preface The construction of Ocelot + consult has been completed in the previous article (5) – Ocelot API gateway (2) of. Net core microservices introduction. This article briefly introduces the eventbus. Eventbus – event […]

  • Android serial 23 – Cross program broadcast, orderly broadcast


    1、 Broadcasting across programs Broadcast is a kind of cross process communication mode; Let’s write a project to send an orderly broadcast Start with a broadcasttest3 project Then write a class to receive broadcast, inherited from broadcastreceiver package com.example.broadcasttest3; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.widget.Toast; public class AnotherBroadcastReceiver extends BroadcastReceiver { @Override public […]

  • The parent component listens to the lifecycle of a child component


    If the parent component is listening to the child component mountmountedDo some logical processing 1. Useonand”>On and emit Sub componentsemittouchhairOneindividualmatterpiece,fathergrouppiece”>emittouchhairOneindividualmatterpiece,fathergrouppieceEmit triggers an event, and the parent component on listens for the corresponding event. // Parent.vue // Child.vue mounted() { this.$emit(“mounted”); } 2. Hook function This is a particularly simple way. The child component does not […]

  • Java process control: sequential structure


    1、 Process control In JavaProcess control statementIt can be classified as follows:Sequence structure, choice structure and circulation structure。 These three structures are enough to solve all the problems! 2、 Sequential structure Description: Java process controlBasic structureIt’s a sequential structure. Unless otherwise specified, java code isIn order, statements and code blocks are executed from top to […]

  • Explain in MySQL


    explainExplain simulates the optimizer to execute SQL statements. In 5.6 and later versions, except for select, others such as insert, update and delete can use explain to view the execution plan, so as to know how MySQL processes SQL statements and analyze the performance bottlenecks of query statements or table structures.effect1. Read order of tables2. […]

  • Link multi stream join


    Multi stream join The semantics of the real-time computed join and the traditional batch join are consistent, both of which are used to link the two tables. The difference is that the real-time calculation links two dynamic tables, and the result of the connection is also dynamically updated to ensure that the final result is […]

  • MySQL big table pagination (with unique secret technique)


      Background of the problem The order table in MySQL (InnoDB) needs to be paged and queried in chronological order, and the primary key is not incremental in time dimension. The order table is more than one million in size. How to effectively realize this requirement? Note: This article does not mainly explain how to […]

  • Pit! Just wrote a line of SQL, and the whole system hung up


    Author: different technology housesource: juejin.im/post/5e670f0151882549274a65ef preface Insert into select. On this day, XXX received a request to migrate the data in table a to table B for backup. This would like to find out through the program, and then batch insert. However, XXX felt that it was a bit slow and required a lot of […]

  • A picture is a complete explanation


    Explain keyword can simulate the MySQL optimizer to execute SQL statements, and can analyze the performance bottleneck of SQL statements or table structure. Use of explain 1. What is the reading order of the table 2. What are the types of data reading operations 3. Which indexes can be used 4. Which indexes are actually […]

  • Redis processes the business after the invalid time effective key to replace the scheduled task query


    Redis sets the invalid key, which provides a convenient function. After adding redis monitoring, it can partially replace the scheduled task; Take a simple example If the order is not paid, it will be cancelled after 30 minutes, and the order status will be changed. In general, regular tasks query orders that are not paid […]