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Insert, on duplicate update in PostgreSQL?
...propriate:
CREATE TABLE db (a INT PRIMARY KEY, b TEXT);
CREATE FUNCTION merge_db(key INT, data TEXT) RETURNS VOID AS
$$
BEGIN
LOOP
-- first try to update the key
-- note that "a" must be unique
UPDATE db SET b = data WHERE a = key;
IF found THEN
RET...
HTML5 Canvas vs. SVG vs. div
What is the best approach for creating elements on the fly and being able to move them around? For example, let's say I want to create a rectangle, circle and polygon and then select those objects and move them around.
...
AngularJS- Login and Authentication in each route and controller
... down in 3 parts: the state of the user is stored in a service, in the run method you watch when the route changes and you check if the user is allowed to access the requested page, in your main controller you watch if the state of the user change.
app.run(['$rootScope', '$location', 'Auth', functi...
Spinlock versus Semaphore
...r mainly in four things:
1. What they are
A spinlock is one possible implementation of a lock, namely one that is implemented by busy waiting ("spinning"). A semaphore is a generalization of a lock (or, the other way around, a lock is a special case of a semaphore). Usually, but not necessarily, sp...
Possible heap pollution via varargs parameter
...s.get(0);
@SafeVarargs does not prevent this at all. However, there are methods which provably will not pollute the heap, the compiler just can't prove it. Previously, callers of such APIs would get annoying warnings that were completely pointless but had to be suppressed at every call site. Now ...
Java code To convert byte to Hexadecimal
...ral answers here uses Integer.toHexString(int); this is doable, but with some caveats. Since the parameter is an int, a widening primitive conversion is performed to the byte argument, which involves sign extension.
byte b = -1;
System.out.println(Integer.toHexString(b));
// prints "fff...
When should the volatile keyword be used in C#?
...h problems does it solve and which it doesn't? In which cases will it save me the use of locking?
10 Answers
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GUI not working after rewriting to MVC
I'm practicing MVC style programming. I have a Mastermind game in a single file, working fine (maybe apart of the fact that "Check" button is invisible at start).
...
Difference between git pull and git pull --rebase
I started using git sometime back and do not fully understand the intricacies. My basic question here is to find out the difference between a git pull and git pull --rebase , since adding the --rebase option does not seem to do something very different : just does a pull.
...
What does it mean to “program to an interface”?
I have seen this mentioned a few times and I am not clear on what it means. When and why would you do this?
32 Answers
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