• Analyze the difference between basic data types and reference data types in JS from simple to in-depth


    one   Data classification of JS in a broad sense JS is divided into two data types: 1. Basic data type: number, string, null, Bollean, undefined, symbol (ES6) Whether it can be changed: no (when the basic data type is re assigned, it will point to a new memory address, and the old one will […]

  • About common protocols – archiving / de archiving, deep / shallow copy


    NSCoding Many times, we need to save our object in memory to disk to facilitate the next use of this object. Among them, this preservation process is called archive. On the contrary, turning the data in the disk into an object is called UN archive. Unarchive includes the process of converting binary data into objects, […]

  • Mongodb replica set


    1、 Introduction to mongodb Mongodb is a document oriented database. In fact, it is a database between relational and non relational. In the world of mongodb, there is no row concept. Instead, the document model is used. Documents and arrays can be embedded in documents, which is very flexible. It supports JSON and bson data […]

  • [Alibaba cloud EMR actual combat] take EMR test cluster version as an example to explain the steps of using Flink SQL client to integrate hive


    Brief introduction: take the test cluster version as an example (emr-4.4.1) — Flink SQL client integrated hive use documentAuthor: Lin Zhicheng, technical support of Alibaba cloud EMR product team, has many years of open source big data experience 1. Take the test cluster version as an example (emr-4.4.1) 2. The execution order is as follows […]

  • Cold backup and hot backup of MySQL


    Cold backup and hot backup of MySQL 1、 Cold backup (off, slow, point in time recovery) Cold backup occurs when the database has been shut down normally. When it is shut down normally, it will provide us with a complete database. Cold backup is a term for copying critical files to another location. Cold backup […]

  • JS to realize deep copy


    catalogue JS implementation Simple deep copy (one shallow copy) Rough deep copy (discard object‘s constructor) Complex deep copy (relatively perfect) Es implementation Clonedeep method in lodash (perfect) 1、 JS implementation 1. Simple deep copy (one layer of shallow copy) ① For circular copy //Copy only the shallow copy of the first layer function simpleCopy(obj1) { […]

  • Copy copies one or more files from one location to another


    copyCopy one or more files from one location to another. grammarcopy [/d] [/v] [/n] [{/y|/-y}] [/z] [{/a|/b}] Source [{/a|/b}] [+ Source [{/a|/b}] [+ …]][Destination [{/a|/b}]] parameter/d  Allows the copied encrypted file to be saved as a decrypted file at the destination.  /v  Verify that the new file is written correctly.  /n  Use short file names (if any) when copying files with names longer than eight characters or file extensions […]

  • Zero copy of Linux and Java


    Linux traditional IO Hello everyone, I am a piece of data lying on the Linux disk. Now to send me from the disk to the network card, I need to go through the following steps: Read operation As shown in the figure above: the operating system divides memory into kernel space and user space. First, […]

  • Fork analysis of Linux process creation


       inLinuxIn the kernel, processes are maintained all the time. From process creation to process destruction, every environment has complex details. IntroductionLinuxHow does the kernel create processesforkThe creation of functions and subprocesses is also crucial for understanding multi process development. catalogue Fork() function Fork() example Virtual address space of parent-child process Fork() function First, let’s […]

  • Java NiO – zero copy


    NiO zero copy Using the traditional IO method to pass a large file Transfer to a large file using NiO zero copy Take a look at the time taken by the two delivery methods Traditional IO method Server code public class OldServer { Client code public class OldClient { NiO zero copy Server code public […]

  • Comparison of mainstream distributed file systems


    This article is long. I suggest you read it carefully, and you will get different results. 1、 Overview Distributed file system is a basic application in distributed field, and the most famous one is undoubtedly HDFS / GFS. Nowadays, the field has become more mature, but understanding its design points and ideas is of great […]

  • Design pattern learning 05 (Java implementation) – prototype pattern


    Write on the front Take notes on learning design patterns Improve the flexible use of design patterns Learning address https://www.bilibili.com/vide… https://www.bilibili.com/vide… Reference article http://c.biancheng.net/view/1… Project source codehttps://gitee.com/zhuang-kang/DesignPattern 6. Prototype mode 6.1 definition and characteristics of prototype model The definition of prototype pattern is as follows:Using an instance that has been created as a prototype, a […]