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Computed / calculated / virtual / derived columns in PostgreSQL
...(Not in Postgres 13, yet) .
Related:
Attribute notation for function call gives error
Until then, you can emulate VIRTUAL generated columns with a function using attribute notation (tbl.col) that looks and works much like a virtual generated column. That's a bit of a syntax oddity which exi...
What is the real overhead of try/catch in C#?
... to make here:
Firstly, there is little or NO performance penalty in actually having try-catch blocks in your code. This should not be a consideration when trying to avoid having them in your application. The performance hit only comes into play when an exception is thrown.
When an exception is th...
Typical .gitignore file for an Android app
...
You can mix Android.gitignore:
# built application files
*.apk
*.ap_
# files for the dex VM
*.dex
# Java class files
*.class
# generated files
bin/
gen/
# Local configuration file (sdk path, etc)
local.properties
with Eclipse.gitignore:
*.pydevproject
.project
.metadata
bin/**
tmp/**
...
javascript scroll event for iPhone/iPad?
... onscroll only after you've stopped scrolling.
The usual way of installing the handler works e.g.
window.addEventListener('scroll', function() { alert("Scrolled"); });
// or
$(window).scroll(function() { alert("Scrolled"); });
// or
window.onscroll = function() { alert("Scrolled"); };
// etc...
What are the downsides to using Dependency Injection? [closed]
...
A couple of points:
DI increases complexity, usually by increasing the number of classes since responsibilities are separated more, which is not always beneficial
Your code will be (somewhat) coupled to the dependency injection framework you use (or more generally how you ...
Quora如何在快速开发中保持高品质代码 - 项目管理 - 清泛网 - 专注C/C++及内核技术
...模块/目录等级的代码“ownership”上添加标签，例如：
__reviewer__ = 'vanessa, kornel'
如果提交新变更，系统就自动会分析文件（或其上层目录），将新审查者的名字添加到提交数据中。我们还有额外的规则将代码审核派发给合适的...
What is the difference between is_a and instanceof?
...ut PHP versions >= 5.3.9 now accept an optional third boolean argument $allow_string (defaults to false) to allow comparisons of string class names instead:
class MyBaseClass {}
class MyExtendingClass extends MyBaseClass {}
// Original behavior, evaluates to false.
is_a(MyExtendingClass::class,...
How to change Vagrant 'default' machine name?
...
I found the multiple options confusing, so I decided to test all of them to see exactly what they do.
I'm using VirtualBox 4.2.16-r86992 and Vagrant 1.3.3.
I created a directory called nametest and ran
vagrant init precise64 http://files.vagrantup.com/precise64.box
to generate a...
A fast method to round a double to a 32-bit int explained
... this:
and it can be seen as two 32-bit integers; now, the int taken in all the versions of your code (supposing it's a 32-bit int) is the one on the right in the figure, so what you are doing in the end is just taking the lowest 32 bits of mantissa.
Now, to the magic number; as you correctly ...
How can I create a link to a local file on a locally-run web page?
...a>
These will never open the file in your local applications automatically. That's for security reasons which I'll cover in the last section. If it opens, it will only ever open in the browser. If your browser can display the file, it will, otherwise it will probably ask you if you want to down...