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mongodb group values by multiple fields
... $slice just off the basic aggregation result. For "large" results, run parallel queries instead for each grouping ( a demonstration listing is at the end of the answer ), or wait for SERVER-9377 to resolve, which would allow a "limit" to the number of items to $push to an array.
db.books.aggregate(...
How to hash some string with sha256 in Java?
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SHA-256 isn't an "encoding" - it's a one-way hash.
You'd basically convert the string into bytes (e.g. using text.getBytes(StandardCharsets.UTF_8)) and then hash the bytes. Note that the result of the hash would also be arbitrary binary data, and if you want to represent that in a strin...
Hadoop “Unable to load native-hadoop library for your platform” warning
...e native Hadoop library $HADOOP_HOME/lib/native/libhadoop.so.1.0.0 was actually compiled on 32 bit.
Anyway, it's just a warning, and won't impact Hadoop's functionalities.
Here is the way if you do want to eliminate this warning, download the source code of Hadoop and recompile libhadoop.so.1.0....
What is the difference between partitioning and bucketing a table in Hive ?
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Partitioning data is often used for distributing load horizontally, this has performance benefit, and helps in organizing data in a logical fashion. Example: if we are dealing with a large employee table and often run queries with WHERE clauses that restrict the results to a particular ...
Eclipse executable launcher error: Unable to locate companion shared library
I had Eclipse Indigo installed on my computer with the Android plugin and it was working perfectly for about two weeks. Today, I updated java and quicktime then restarted my computer. When it booted back up, eclipse had completely vanished - all the program files have completely disappeared. When I ...
ASP.NET MVC: No parameterless constructor defined for this object
...same exception occurs when a Model has no parameterless constructor.
The call stack was figuring a method responsible for creating a new instance of a model.
System.Web.Mvc.DefaultModelBinder.CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
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Keyboard shortcuts in WPF
I know about using _ instead of & , but I'm looking at all the Ctrl + type shortcuts.
10 Answers
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How to read and write INI file with Python3?
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The standard ConfigParser normally requires access via config['section_name']['key'], which is no fun. A little modification can deliver attribute access:
class AttrDict(dict):
def __init__(self, *args, **kwargs):
super(AttrDict, self).__init...
Add Variables to Tuple
... I think its important to note that tuples are immutable - they cannot actually be modified. What this solution does is create a new tuple based on two existing tuples.
– That1Guy
Jan 16 '19 at 20:58
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How to convert nanoseconds to seconds using the TimeUnit enum?
... This answer is now wrong - convert() and the toFoo() methods all return longs now docs.oracle.com/javase/6/docs/api/java/util/concurrent/…
– Riking
Jul 30 '13 at 1:58
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