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Android: upgrading DB version and adding new table
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1. About onCreate() and onUpgrade()
onCreate(..) is called whenever the app is freshly installed. onUpgrade is called whenever the app is upgraded and launched and the database version is not the same.
2. Incrementing the db version
You need a constructor like:
MyOpenHelp...
Fastest way to get the first object from a queryset in django?
...eturn None if there aren't any. There are lots of ways to do this which all work. But I'm wondering which is the most performant.
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Is there a REAL performance difference between INT and VARCHAR primary keys?
... and a coworker won't budge on the INT AUTO_INCREMENT as a primary key for all tables.
14 Answers
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How can you make a custom keyboard in Android?
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First of all you will need a keyboard.xml file which will be placed in the res/xml folder (if the folder does not exist, created it).
<?xml version="1.0" encoding="utf-8"?>
<Keyboard xmlns:android="http://schemas.android.com...
How to wait for several Futures?
...ave several futures and need to wait until either any of them fails or all of them succeed.
8 Answers
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Average of 3 long integers
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This code will work, but isn't that pretty.
It first divides all three values (it floors the values, so you 'lose' the remainder), and then divides the remainder:
long n = x / 3
+ y / 3
+ z / 3
+ ( x % 3
+ y % 3
+ z % 3
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How do I capture SIGINT in Python?
...f KeyboardInterruptException is implemented as a SIGINT handler or if it really only catches Ctrl+C presses, but either way, using a signal handler makes your intent explicit (at least, if your intent is the same as OP's). More importantly though, with a signal you don't have to wrap try-catches ar...
Try catch statements in C
... exceptions but you can simulate them to a degree with setjmp and longjmp calls.
static jmp_buf s_jumpBuffer;
void Example() {
if (setjmp(s_jumpBuffer)) {
// The longjmp was executed and returned control here
printf("Exception happened here\n");
} else {
// Normal code execution s...
Union of dict objects in Python [duplicate]
...yptic, and it immediately makes most readers balk and the remainder assume all the keys in x would have to be legal parameter names. IMHO, the fact it works is a bug in the name-checking mechanisms in the implementation. What happens when you rely on bugs? They either get fixed, or become politic...
Why do I need an IoC container as opposed to straightforward DI code? [closed]
...ain can become nested, and it quickly becomes unwieldy to wire them up manually. Even with factories, the duplication of your code is just not worth it.
IoC containers can be complex, yes. But for this simple case I've shown it's incredibly easy.
Okay, let's justify this even more. Let's say ...