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mongoDB/mongoose: unique if not null
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As of MongoDB v1.8+ you can get the desired behavior of ensuring unique values but allowing multiple docs without the field by setting the sparse option to true when defining the index. As in:
email : {type: String, trim: true, index: true, unique...
Which is best way to define constants in android, either static class, interface or xml resource?
I'm developing an android application which uses web service to get data from server, for that I'm having three different set of URLs to point development system, test server and live server. It's difficult to change URL whenever I want to give application for testing/live. so I planned to make it a...
What is a Manifest in Scala and when do you need it?
Since Scala 2.7.2 there is something called Manifest which is a workaround for Java's type erasure. But how does Manifest work exactly and why / when do you need to use it?
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Build the full path filename in Python
...e + "." + filename_suffix)
Keep in mind that os.path.join() exists only because different operating systems use different path separator characters. It smooths over that difference so cross-platform code doesn't have to be cluttered with special cases for each OS. There is no need to do this for fi...
Which concurrent Queue implementation should I use in Java?
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Basically the difference between them are performance characteristics and blocking behavior.
Taking the easiest first, ArrayBlockingQueue is a queue of a fixed size. So if you set the size at 10, and attempt to insert an 11th el...
Why is rbindlist “better” than rbind?
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rbindlist is an optimized version of do.call(rbind, list(...)), which is known for being slow when using rbind.data.frame
Where does it really excel
Some questions that show where rbindlist shines are
Fast vectorized merge of list of data.frames by row
Troubl...
How to create a density plot in matplotlib?
In R I can create the desired output by doing:
5 Answers
5
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What is the difference between Pan and Swipe in iOS?
...ween pan and swipe. Most likely, your pan recognizer "wins" the conflict because its gesture is simpler / more general: A swipe is a pan but a pan may not be a swipe, so the pan recognizes first and excludes other recognizers.
You should be able to resolve this conflict using the delegate method ge...
ASP.NET MVC A potentially dangerous Request.Form value was detected from the client when using a cus
...usages of the default modelbinder.
Custom ModelBinder
It appears that a call to bindingContext.ValueProvider.GetValue() in the code above always validates the data, regardless any attributes. Digging into the ASP.NET MVC sources reveals that the DefaultModelBinder first checks if request validat...
Adding up BigDecimals using Streams
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Obtain a List<BigDecimal>.
Turn it into a Stream<BigDecimal>
Call the reduce method.
3.1. We supply an identity value for addition, namely BigDecimal.ZERO.
3.2. We specify the BinaryOperator<BigDecimal>, which adds two BigDecimal's, via a method reference BigDecimal::add.
Upd...