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Postgres: INSERT if does not exist already
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Postgres 9.5 (released since 2016-01-07) offers an "upsert" command, also known as an ON CONFLICT clause to INSERT:
INSERT ... ON CONFLICT DO NOTHING/UPDATE
It solves many of the subtle problems you can run into when using concurrent operation, which some other answers propose.
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Why are all fields in an interface implicitly static and final?
I am just trying to understand why all fields defined in an Interface are implicitly static and final . The idea of keeping fields static makes sense to me as you can't have objects of an interface but why they are final (implicitly)?
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How to increase timeout for a single test case in mocha
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timeout is in milliseconds, and it defaults 2000.
– Ethan Mick
Oct 26 '14 at 4:10
47
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If a DOM Element is removed, are its listeners also removed from memory?
...element itself is picked up by the garbage collector as well as any event handlers/listeners associated with it.
var a = document.createElement('div');
var b = document.createElement('p');
// Add event listeners to b etc...
a.appendChild(b);
a.removeChild(b);
b = null;
// A reference to 'b' no lon...
How do I check for C++11 support?
...amed __cplusplus that C++ compilers should set to the version of the C++ standard supported see this
#if __cplusplus <= 199711L
#error This library needs at least a C++11 compliant compiler
#endif
It is set to 199711L in Visual Studio 2010 SP1, but I do not know if vendors will be so bold to...
Dealing with nginx 400 “The plain HTTP request was sent to HTTPS port” error
...a app behind passenger/nginx. I'm trying to get it to respond to both http and https calls. The problem is, when both are defined in the server block https calls are responded to normally but http yields a 400 "The plain HTTP request was sent to HTTPS port" error. This is for a static page so I'm gu...
How to get the first non-null value in Java?
...(i != null) return i;
return null;
}
For efficient reasons, you can handle the common cases as follows:
public static <T> T coalesce(T a, T b) {
return a == null ? b : a;
}
public static <T> T coalesce(T a, T b, T c) {
return a != null ? a : (b != null ? b : c);
}
public s...
What is “Argument-Dependent Lookup” (aka ADL, or “Koenig Lookup”)?
...s how unqualified names are looked up by the compiler in C++.
The C++11 standard § 3.4.2/1 states:
When the postfix-expression in a function call (5.2.2) is an unqualified-id, other namespaces not considered during the usual unqualified lookup (3.4.1) may be searched, and in those namespaces, ...
How to check if a specific key is present in a hash or not?
... edited Jun 12 '17 at 19:44
Andre Figueiredo
10k66 gold badges3939 silver badges6767 bronze badges
answered Aug 21 '13 at 13:09
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What is the significance of #pragma marks? Why do we need #pragma marks?
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#pragma mark is used to tag the group of methods so you may easily find and detect methods from the Jump Bar. It may help you when your code files reach about 1000 lines and you want to find methods quickly through the category from Jump box.
In a long program it becomes difficult to remember an...