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How do I perform the SQL Join equivalent in MongoDB?
...rect. The new $lookup operator added to the aggregation pipeline is essentially identical to a left outer join:
https://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <...
Dynamically set local variable [duplicate]
How do you dynamically set local variable in Python (where the variable name is dynamic)?
7 Answers
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How to implement __iter__(self) for a container object (Python)
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I normally would use a generator function. Each time you use a yield statement, it will add an item to the sequence.
The following will create an iterator that yields five, and then every item in some_list.
def __iter__(self):
...
How exactly does __attribute__((constructor)) work?
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It runs when a shared library is loaded, typically during program startup.
That's how all GCC attributes are; presumably to distinguish them from function calls.
GCC-specific syntax.
Yes, this works in C and C++.
No, the function does not need to be static.
The destructo...
Elasticsearch query to return all records
I have a small database in Elasticsearch and for testing purposes would like to pull all records back. I am attempting to use a URL of the form...
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How to check SQL Server version
...ndows NT 6.1 <X64> (Build 7600: )
As you can see, this entry gives all the necessary information about the product, such as version, product level, 64-bit versus 32-bit, the edition of SQL Server, and the OS version on which SQL Server is running.
Method 4: Connect to the instance of SQL Se...
Why does ReSharper tell me “implicitly captured closure”?
... use.
The compiler generates a class for both lambda expressions and puts all variables in that class which are used in the lambda expressions.
So in my example g and i are held in the same class for execution of my delegates. If g is a heavy object with a lot of resources left behind, the garbage...
Extract public/private key from PKCS12 file for later use in SSH-PK-Authentication
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This is possible with a bit of format conversion.
To extract the private key in a format openssh can use:
openssl pkcs12 -in pkcs12.pfx -nocerts -nodes | openssl rsa > id_rsa
To convert the private key to a public key:
openssl...
Python read-only property
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Generally, Python programs should be written with the assumption that all users are consenting adults, and thus are responsible for using things correctly themselves. However, in the rare instance where it just does not make sens...
How do JavaScript closures work?
...clared outside the function, regardless of when and where the function is called.
If a function was called by a function, which in turn was called by another function, then a chain of references to outer lexical environments is created. This chain is called the scope chain.
In the following code, in...