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Random record from MongoDB
...m the mycoll collection.
db.mycoll.aggregate([{ $sample: { size: 1 } }])
If you want to select the random document(s) from a filtered subset of the collection, prepend a $match stage to the pipeline:
// Get one random document matching {a: 10} from the mycoll collection.
db.mycoll.aggregate([
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How to install a specific version of a ruby gem?
Using the command-line gem tool, how can I install a specific version of a gem?
6 Answers
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How to keep index when using pandas merge
... I do the merge, the resulting DataFrame has integer index. How can I specify that I want to keep the index from the left data frame?
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How to handle Objective-C protocols that contain properties?
...l, they have no variables or methods themselves - they only describe a specific set of attributes that is true about your class so that objects holding references to them can use them in specific ways.
That means in your class that conforms to your protocol, you have to do everything to make sure a...
How to recover a dropped stash in Git?
...mal tools. When you’re done, just blow the branch away.
Finding the hash
If you have only just popped it and the terminal is still open, you will still have the hash value printed by git stash pop on screen (thanks, Dolda).
Otherwise, you can find it using this for Linux, Unix or Git Bash for Wind...
Select2 doesn't work when embedded in a bootstrap modal
...r the focused element is either the overlay itself or a descendent of it - if not it just refocuses on the overlay. With the select2 dropdown being attached to the body this effectively prevents you from entering anything into the the textfield.
You can quickfix this by overwriting the enforceFocus ...
Should *.xccheckout files in Xcode5 be ignored under VCS?
...ies, the presence of an .xccheckout file in the workspace allows Xcode to know what all of the components that make up a workspace are and where to get them.
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Why does pattern matching in Scala not work with variables?
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What you're looking for is a stable identifier. In Scala, these must either start with an uppercase letter, or be surrounded by backticks.
Both of these would be solutions to your problem:
def mMatch(s: String) = {
val target: String = "a"
s match {
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Techniques for Tracing Constraints
... b ~ sup,
SyntacticN (a -> (a -> b) -> b) fi,
_)
=> a -> (a -> b) -> a
share = sugarSym Let
The key is to use type hole among constraints: _ => your difficult type
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10 条真心有趣的 Linux 命令 - 创意 - 清泛网 - 专注C/C++及内核技术
...rank@crank-System:~$ sudo apt-get install fortune
利用fortune命令的_s选项，他会限制一个句子的输出长度。
# fortune -s
3.yes
# yes <string>
这个命令会不停打印字符串，直到用户把这进程给结束掉。
# yes unixmen
4.figlet
这个命令可以...