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  MySQL Index Merge Optimization Practices

In production environment databases, it is often seen that some SQL where conditions include: equal condition on a normal index + primary key range query + order by limit Although using a normal index would be more efficient, the system chooses to use index merge instead in some cases. This article explores such index merge situations. Index Merge Official Introduction   The Index Merge access method retrieves rows with multiple range scans and merges their results into one. Generall...

   INDEX MERGE,MYSQL,PRIMARY INDEX,SECONDARY INDEX     2024-09-10 04:52:26

  A Python assignment trap

Python has no assignment, it only has reference. Assume, we have following code snippet: >>> values = [0, 1, 2] >>> values[1] = values >>> values [0, [...], 2] Why the result is not [0, [0, 1, 2], 2], instead it goes into an infinite loop? To understand this, we need to understand some basics about Python. Python has no variables, it only has labels. When we run: values = [0, 1, 2] Python will first create a list object [0,1,2], then it labels it as values. If we later...

   Python,Assignment,Trap,Shallow copy     2013-07-19 22:08:36

  Database Testing – Practical Tips and Insight on How to Test Database

Database is one of the inevitable parts of a software application these days. It does not matter at all whether it is web or desktop, client server or peer to peer, enterprise or individual business, database is working at backend. Similarly, whether it is healthcare of finance, leasing or retail, mailing application or controlling spaceship, behind the scene a database is always in action. Moreover, as the complexity of application increases the need of stronger and secure database emerge...

   Database,Tips,Practice     2011-06-29 08:47:40

  Best practices of front end optimization

1. Use DocumentFragment or innerHTML to replace complex elements insertion DOM operation on browser is expensive. Although browser performance is improved much, multiple DOM elements insertion is still expensive and will affect the page load speed. Assume we have an ul element on our page, we now want to retrieve a JSON list using AJAX and then update the ul using JavaScript. Usually we may write it as : var list = document.querySelector('ul'); ajaxResult.items.forEach(function(item) { // ...

   JavaScript,Front end,Optimization,Tips     2013-07-06 11:26:27

  Can a === 1 && a === 2 && a === 3 be true in JavaScript?

Lots of you may be aware that there is famous interview question which asks whether a == 1 && a == 2 && a == 3 can be true in JavaScript. And the answer to this question is YES. The reason is that == will do a non-strict comparison which will evaluate a to a number and this provides the possibility of dynamically return the value when every time a is accessed. Have you ever wondered whether a === 1 && a === 2 && a === 3 can be true? At first glance, it seems this ...

   JAVASCRIPT,===,STRICT COMPARISON     2018-04-06 12:17:29

  Multitasking vs multiprogramming

As all these processing are the part of computer functions. You should not be confused between these processes.In computing, multitasking is a method by which multiple tasks are performed by the user also known as processes, share common processing resources such as a CPU. CPU is actively executing more than one task at a time. Multitasking solves the problem by scheduling the tasks instructions. Which task may be the one running at any...

   multitasking,multiprogramming,os,differe     2011-09-22 13:46:30

  JavaScript cross domain request solution

1. What is cross domain? We may often using AJAX to request data from other domain, now we will have cross domain request issues. It's because JavaScript only allows to request data from the same domain because of security consideration. In short, same domain strategy means a piece of code can read data from the same source, the same source here means the combination of the same domain, protocol and port number. For example: URLDescriptionAllow communication? http://www.a.com/a.js http:/...

   AJAX,cross domain,security     2013-03-13 20:04:52

  Event Loop Mechanism in JavaScript

Introduction The Event Loop Mechanism The event loop mechanism is the core of how JavaScript handles asynchronous operations. It ensures that the execution order of the code aligns with the expected sequence. JavaScript's Single Thread JavaScript is known for being a single-threaded language, meaning it executes one task at a time. This can lead to a significant issue: if a thread is blocked, the entire program becomes unresponsive. To address this, JavaScript introduced the event loop mechanism...

   JAVASCRIPT,EVENT MECHANISM,EVENT LOOP     2024-07-03 08:19:09

  Best Rich Text Editors ready to use in web projects

This post illustrates five interesting rich text editors ready to use in your web projects. I also provided some guidelines regarding how to implement them on your pages using a few lines of HTML code. Try them!1. Yahoo! UI Library: Rich Text EditorThe Yahoo! Rich Text Editor is a UI control that replaces a standard HTML textarea and is based on Yahoo! UI Library; it allows for the rich formatting of text content, including common structural treatments like lists, formatting treatments like...

   RTE,Example,Project,Open Source,Best,Sim     2011-07-27 10:57:33

  JavaScript efficiency catch up

JavaScript is a very flexible language, we can write JavaScript code freely with various styles, different kinds of codes will have different execution efficiency. Here we summarize some tips we get from our development. Efficiency of JavaScript itself JavaScript has execution context chain, closures, prototype inheritance, eval etc. It brings us some magic features, but it also introduces the performance issue, if we don't use them properly, it will affect the codes execution efficiency. 1. Glo...

   JavaScript,efficiency,event delegation,eval     2013-04-02 04:08:46

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