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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
... Wheel
This reduces the number of round-trips to the database from N+1 to 2.
Most ORM tools give you several ways to prevent N+1 selects.
Reference: Java Persistence with Hibernate, chapter 13.
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Convert light frequency to RGB?
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answered Sep 24 '09 at 15:47
Stephen MesaStephen Mesa
4,31333 gold badges2121 silver badges1616 bronze badges
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Find the nth occurrence of substring in a string
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21 Answers
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Get the first element of each tuple in a list in Python [duplicate]
...[x[0] for x in rows]
Below is a demonstration:
>>> rows = [(1, 2), (3, 4), (5, 6)]
>>> [x[0] for x in rows]
[1, 3, 5]
>>>
Alternately, you could use unpacking instead of x[0]:
res_list = [x for x,_ in rows]
Below is a demonstration:
>>> lst = [(1, 2), (...
Numpy argsort - what is it doing?
... to the documentation
Returns the indices that would sort an array.
2 is the index of 0.0.
3 is the index of 0.1.
1 is the index of 1.41.
0 is the index of 1.48.
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Disable a group of tests in rspec?
... in the output:
before { skip("Awaiting a fix in the gem") }
with RSpec 2:
before { pending }
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Join a list of items with different types as string in Python
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answered Aug 28 '10 at 9:09
Mark ByersMark Byers
683k155155 gold badges14681468 silver badges13881388 bronze badges
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How do I immediately execute an anonymous function in PHP?
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121
For PHP7: see Yasuo Ohgaki's answer: (function() {echo 'Hi';})();
For previous versions: the o...
Can you have if-then-else logic in SQL? [duplicate]
...e1 WHERE project = 1
ELSE IF ((SELECT COUNT(*) FROM table1 WHERE project = 2) > 0)
SELECT product, price FROM table1 WHERE project = 2
ELSE IF ((SELECT COUNT(*) FROM table1 WHERE project = 3) > 0)
SELECT product, price FROM table1 WHERE project = 3
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