SEARCH KEYWORD -- Data mining


  Guide on recovering data in MySQL

In our daily work, there might be mistakes made which got some data or even databases deleted in MySQL. If this happens on production, it would be a nightmare. In case this happens, normally DBA would jump in to save the world. And they would try to recover the data from the backup if there is any. But if there is no backup, then the show stops. Hence database backup is necessary on production environments to avoid such awkward situation. Also normally in MySQL, binlog should be enabled as well ...

   MYSQL,DATABASE,BACKUP,BINLOG,EXAMPLE     2020-08-26 07:50:30

  Use of Erlang in WhatsApp

After many years, people are still discussing whether Erlang is a small language. People have all sorts of doubt about it, but with the appearance of WhatsApp, we may change our mind. What is WhatsApp, from its official website: WhatsApp Messenger is a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. The more funny thing is the main developer of WhatsApp Rick Reed worked in Yahoo and SGI before he joined WhatsApp and he didn't have any know...

   Erlang,WhatsApp,Architecture     2013-06-16 03:03:46

  Understand unsafe in GoLang

Before going to understand unsafe package in GoLang, the first thing needs to talk about is the pointer in GoLang. If you have a background of C language, you must know what pointer means and its usage. With pointer, you are free to operate any data at memory level which means you have great power, but this means that you have great responsibility as well. That's why it might be considered unsafe in lots of cases. Take a look at a simple example of doubling an integer. package main import "fmt"...

   GOLANG,UNSAFE,ZERO-COPY     2020-03-14 23:18:00

  Output control functions in PHP

The Output Control functions in PHP allow you to control when output is sent from the script. This can be useful in several different situations, especially if you need to send headers to the browser after your script has began outputting data. The Output Control functions do not affect headers sent using header() or setcookie(), only functions such as echo and data between blocks of PHP code. These output control functions include ob_start(0, ob_clean(),ob_get_contents(), etc. To be honest, I a...

   PHP,output buffer,relationship,ob     2012-06-15 10:11:58

  How to choose JavaScript template engine?

With the increase of density of web front end development, AJAX and JSON are used more and more frequently, it's necessary to use many tags in front end development. You may have a JSON object as below: var data={  email: 'terry.li@gbin1.com,  gender: 'male'  } Then you need to organize the JSON data into page elements. var email, gender;email= ' ' + data.email+ '; gender= ' ' + data.gender + '; $('#contentwrapper‘).append(content).append(gender); The output is very simple: ...

   JavaScript template engine,Template     2012-10-07 07:03:58

  Apple patent shows they are developing "Killer" 3D Camera

This is not the first time that Apple patent shows they have interest on 3D camera technology. In November last year, one Apple patent shows that Apple is developing advanced three-dimensional object recognition and verification technology. According to PatentlyApple report (March 30,2012) one patent released this week shows that Apple is developing a 3D camera technology for the future iOS devices. This 3D camera is described as an advanced component with advanced micro-lens, depth, chrom...

   3D Camera,Apple,Patent     2012-04-03 07:46:35

  When will resizing be triggered in Java HashMap?

HashMap is one of the most frequently used collection types in Java, it stores key-value pairs. Ideally it expects to use hash table which expects the data access time complexity to be O(1), however, due to hash conflicts, in reality, it uses linked list or red-black tree to store data which makes the worst case time complexity to be O(logn).  Although collections are using data structures like arrays and linked lists, unlike arrays, they will dynamically resize when there is not enough spa...

   JAVA,RESIZE,HASHMAP,THRESHOLD     2020-05-02 20:41:19

  WireGuard VPN: Setup WG_VPN client App on Android phone and connect to local WG_VPN server on VM

We will show the detail steps about how to setup the WireGuard VPN client on an Android phone/pad and configure the VPN client to connect a WG_VPN server in local network. The setup process contents three main steps: Install WireGuard and create a key-pair in WireGuard client. Add the Android client peer information in the WireGuard server’s config file. Config the Android WireGuard client to connect to the server. The test environment network configuration:  Step 1. Install Wire...

   WIREGUARD,VPN,TUTORIAL     2020-10-24 08:46:42

  How does MySQL handle DROP TABLE

A few days ago, when executing DROP TABLE in MySQL, all processes including DDL and DML were hung until DROP TABLE was completed. I am confused about this phenomenon. I have reviewed the source codes of MySQL to check how MySQL internally handle DROP TABLE. When user trigger DROP TABLE command: ########################MySQL SERVER drop table######################## /* Sql_table.cc  delete (drop) tables. */bool mysql_rm_table( )   /*   Execute the drop of a normal or temporary...

   MySQL,DROP TABLE     2012-09-24 11:34:05

  CASSANDRA data model

Cassandra is an open source distributed database, it combines dynamic key/value and column oriented feature of Bigtable. Features of Cassandra are: Flexible schema, no need to design schema first, it's very convenient to add or delete strings Support range search on keys High usability, extensible. The single node error will not affect the cluster. We can think Cassandra's data model as a 4 or 5 dimensional Hash. COLUMN Columns is the smallest data unit in Cassandra, it is a 3 dimensional data...

   Cassandra,database,sort     2013-06-08 22:07:40

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