大约有 44,000 项符合查询结果（耗时：0.0381秒） [XML]
Index on multiple columns in Ruby on Rails
...
The order does matter in indexing.
Put the most selective field first, i.e. the field that narrows down the number of rows fastest.
The index will only be used insofar as you use its columns in sequence starting at the beginning. i.e. if you index on [:user_id, :article_id...
Wolfram's Rule 34 in XKCD [closed]
...ur of rule 34: http://atlas.wolfram.com/01/01/34/
Hilighted rules (Wolfram selection): http://atlas.wolfram.com/01/01/
Index of all 256 rules: http://atlas.wolfram.com/01/01/rulelist.html
The book contains thousands of nice little diagrams.
...
Suppress warning “Category is implementing a method which will also be implemented by its primary cl
...is answer should be the correct one. Anyway it has more votes than the one selected as answer.
– Juan Catalan
Nov 5 '14 at 17:28
|
show 11 m...
Status bar and navigation bar appear over my view's bounds in iOS 7
...7 SDK. Please add the following code to achieve this,
if ([self respondsToSelector:@selector(edgesForExtendedLayout)])
self.edgesForExtendedLayout = UIRectEdgeNone;
You need to add the above in your -(void)viewDidLoad method.
iOS 7 brings several changes to how you layout and customiz...
Renaming a virtualenv folder without breaking it
...ate_this.py instead of using the
location of the Python interpreter to
select the environment.
Note: you must run this after you've
installed any packages into the
environment. If you make an
environment relocatable, then install
a new package, you must run virtualenv
--relocatabl...
Non greedy (reluctant) regex matching in sed?
...nswering your question
Using approach #2 (delimited expression) you should select two appropriate expressions:
EDE: [^:/]\/
SDE: http:
Usage:
$ sed 's/\([^:/]\/\).*/\1/g; s/\(\(http:.*\)*.\)*/\1/' <<< 'http://www.suepearson.co.uk/product/174/71/3816/'
Output:
http://www.suepearson.co.u...
What are the differences between numpy arrays and matrices? Which one should I use?
...nces between matrix objects and ndarrays
(having to do with np.ravel, item selection and sequence behavior).
The main advantage of numpy arrays is that they are more general than
2-dimensional matrices. What happens when you want a 3-dimensional array? Then
you have to use an ndarray, not a matrix ...
what is the most efficient way of counting occurrences in pandas?
...].astype('str').stack().value_counts().sum() which equates to setting each selected column to str type, stacking all individual columns on top, forming basically one column and then doing the value_counts() and sum() on that one column. :) Stack is pretty useful, it might not be the most obvious cho...
How do I create a new branch?
...ow:
Right click on Trunk/ which you will be creating your Branch from:
Select Branch/Tag:
Type in location of your new branch, commit message, and any externals (if your repository has them):
share
|
...
Do I need to disable NSLog before release Application?
...s is through 'edit scheme' -> 'run app name' -> under the tab 'info' select using the drop-down box between debug & release. In the release version you won't see any NSLog output in the debug console !
How does this all work?
first of all, one must know that a preprocessor is relatively ...