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E11000 duplicate key error index in mongodb mongoose
... null value.
In other words, a sparse index is ok with multiple documents all having null values.
sparse indexes
From comments:
Your error says that the key is named mydb.users.$email_1 which makes me suspect that you have an index on both users.email and users.local.email (The former being old an...
In Python, what is the difference between “.append()” and “+= []”?
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In general case append will add one item to the list, while += will copy all elements of right-hand-side list into the left-hand-side list.
Update: perf analysis
Comparing bytecodes we can assume that append version wastes cycles in LOAD_ATTR + CALL_FUNCTION, and += version -- in BUILD_LIST. App...
AsyncTask and error handling on Android
... some other error-string/code) in this variable. When onPostExecute is called, see if this instance-variable is set to some error. If so, show an error message." (From the user "Streets of Boston" groups.google.com/group/android-developers/browse_thread/thread/…)
– OneWor...
How do you trigger a block after a delay, like -performSelector:withObject:afterDelay:?
Is there a way to call a block with a primitive parameter after a delay, like using performSelector:withObject:afterDelay: but with an argument like int / double / float ?
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Remove Object from Array using JavaScript
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This however will remove all the occurrences found, not only the first one
– Flavien Volken
Jul 12 '16 at 6:49
6
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Reading a UTF8 CSV file with Python
...method gets applied to a Unicode string to make a byte-string; but you're calling it on a byte-string instead... the wrong way 'round! Look at the codecs module in the standard library and codecs.open in particular for better general solutions for reading UTF-8 encoded text files. However, for the ...
Parallel.ForEach() vs. foreach(IEnumerable.AsParallel())
...takes the anonymous delegate, and runs multiple threads on this code in parallel for all the different items.
The second one not very useful in this scenario. In a nutshell it is intended to do a query on multiple threads, and combine the result, and give it again to the calling thread. So the code...
node.js hash string?
... If I have lots of strings to hash, it is less efficient to keep calling crypto.createHash instead of somehow re-using the result?
– Michael
Mar 28 '19 at 3:23
add a ...
Swift variable decorations with “?” (question mark) and “!” (exclamation mark)
I understand that in Swift all variables must be set with a value, and that by using optionals we can set a variable to be set to nil initially.
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Enumerable.Empty() equivalent for IQueryable
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@Nauman - you actually create an [empty] T array - no new object of T is actually created.
– zastrowm
Feb 20 '14 at 15:56
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