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PostgreSQL: Difference between text and varchar (character varying)
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There is no difference, under the hood it's all varlena (variable length array).
Check this article from Depesz: http://www.depesz.com/index.php/2010/03/02/charx-vs-varcharx-vs-varchar-vs-text/
A couple of highlights:
To sum it all up:
char(n) – takes t...
Difference between \w and \b regular expression meta characters
...chor like the caret and the dollar sign. It matches at a position that is called a "word boundary". This match is zero-length.
There are three different positions that qualify as word boundaries:
Before the first character in the string, if the first character is
a word character.
After the last ...
Postfix日常维护队列管理 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...删除。
例如id是0EAF3A9B 那么postsuper -d 0EAF3A9B
postsuper -d ALL 删除所有邮件
显示信件列表：postqueue -p
显示信件內容：postcat -q Queue_ID
刪除各別信件：postsuper -d Queue_ID
全部刪除：postsuper -d ALL
扣住信件：postsuper -h Queue_ID
回复...
How to filter files when using scp to copy dir recursively?
I need to copy all the .class files from server to local with all dir reserved. e.g. server:/usr/some/unknown/number/of/sub/folders/me.class will be /usr/project/backup/some/unknown/number/of/sub/folders/me.class the problem is, there are many other useless files such as .svn-base files that i d...
Best way to change the background color for an NSView
...t—it won't composite on top of any ancestor views. For fills with a partially- (or fully-)transparent color, use NSRectFillUsingOperation developer.apple.com/mac/library/documentation/Cocoa/Reference/… with the NSCompositeSourceOver operation.
– Peter Hosey
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几个有趣的Javascript Hack - 创意 - 清泛网 - 专注C/C++及内核技术
...当前网页已经变成编辑模式了。将上述代码中的true改成false重新执行一遍即可恢复。
2. 舞动的图片
javascript：R=0; x1=.1; y1=.05; x2=.25; y2=.24; x3=1.6; y3=.24; x4=300; y4=200; x5=300; y5=200; DI=document.images; DIL=DI.length; function A(){for(i=0; i-DIL;...
Only read selected columns
...g","Sep","Oct","Nov","Dec"))
dat <- fread("data.txt", drop = c(8:13))
All result in:
> data
Year Jan Feb Mar Apr May Jun
1 2009 -41 -27 -25 -31 -31 -39
2 2010 -41 -27 -25 -31 -31 -39
3 2011 -21 -27 -2 -6 -10 -32
UPDATE: When you don't want fread to return a data.table, use the data.ta...
How do I force “git pull” to overwrite local files?
... content), these files will not be affected.
First, run a fetch to update all origin/<branch> refs to latest:
git fetch --all
Then, you have two options:
git reset --hard origin/master
OR If you are on some other branch:
git reset --hard origin/<branch_name>
Explanation:
git fetch do...
How do I choose grid and block dimensions for CUDA kernels?
...eads per block should be a round multiple of the warp size, which is 32 on all current hardware.
Each streaming multiprocessor unit on the GPU must have enough active warps to sufficiently hide all of the different memory and instruction pipeline latency of the architecture and achieve maximum throu...
Python matplotlib multiple bars
How to plot multiple bars in matplotlib, when I tried to call the bar function multiple times, they overlap and as seen the below figure the highest value red can be seen only.
How can I plot the multiple bars with dates on the x-axes?
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