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How to implement a unique index on two columns in rails
I have a table and I'm trying to add a unique index on two columns. Those columns are also indexed. So my question is if I just can remove the indexes who were just for one column or if I have to use all three indexes:
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Create the perfect JPA entity [closed]
I've been working with JPA (implementation Hibernate) for some time now and each time I need to create entities I find myself struggling with issues as AccessType, immutable properties, equals/hashCode, ... .
So I decided to try and find out the general best practice for each issue and write this ...
2 column div layout: right column with fixed width, left fluid
...right column needs to come before the left one.
If the right has a float (and a width), and if the left column doesn't have a width and no float, it will be flexible :)
Also apply an overflow: hidden and some height (can be auto) to the outer div, so that it surrounds both inner divs.
Finally, at...
How to sort with lambda in Python
In Python, I am trying to sort by date with lambda. I can't understand my error message. The message is:
4 Answers
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TCP 的那些事儿（上） - 更多技术 - 清泛网 - 专注C/C++及内核技术
...，这是一把双刃剑。
SACK 方法
另外一种更好的方式叫：Selective Acknowledgment (SACK)（参看RFC 2018），这种方式需要在TCP头里加一个SACK的东西，ACK还是Fast Retransmit的ACK，SACK则是汇报收到的数据碎版。参看下图：
这样，在发送端...
How to load external webpage inside WebView
...anks to this post, I finally found the solution. Here is the code:
import android.app.Activity;
import android.os.Bundle;
import android.webkit.WebResourceError;
import android.webkit.WebResourceRequest;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast...
C++ IDE for Linux? [closed]
...like me — you end up not using them. Here’s just a small and biased selection:
For Python development, there’s PyCharm
For R, there’s RStudio
For JavaScript and TypeScript, there’s Visual Studio Code (which is also a good all-round editor)
And finally, many people love the Sublime Text...
XPath to find elements that does not have an id or class
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Pretty straightforward:
//tr[not(@id) and not(@class)]
That will give you all tr elements lacking both id and class attributes. If you want all tr elements lacking one of the two, use or instead of and:
//tr[not(@id) or not(@class)]
When attributes and eleme...
Jenkins Host key verification failed
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Change to the jenkins user and run the command manually:
git ls-remote -h git@bitbucket.org:person/projectmarket.git HEAD
You will get the standard SSH warning when first connecting to a new host via SSH:
The authenticity of host 'bitbucket.org (20...
How to center icon and text in a android button with width set to “fill parent”
I want to have an Android Button with icon+text centered inside it. I'm using the drawableLeft attribute to set the image, this works well if the button has a width of "wrap_content" but I need to stretch to max width so I use width "fill_parent" . This moves my icon straight to the left of the b...