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COUNT(*) vs. COUNT(1) vs. COUNT(pk): which is better? [duplicate]
...T(field) or COUNT(*), and stick with it consistently, and if your database allows COUNT(tableHere) or COUNT(tableHere.*), use that.
In short, don't use COUNT(1) for anything. It's a one-trick pony, which rarely does what you want, and in those rare cases is equivalent to count(*)
Use count(*) fo...
What is a “cache-friendly” code?
...her end of the memory spectrum (DRAM), the memory is very cheap (i.e. literally millions of times cheaper) but takes hundreds of cycles after a request to receive the data. To bridge this gap between super fast and expensive and super slow and cheap are the cache memories, named L1, L2, L3 in decre...
Underscore vs Double underscore with variables and methods [duplicate]
...
Explanation:
People coming from a C++/Java background are especially prone to
overusing/misusing this "feature". But __private names don't work the
same way as in Java or C++. They just trigger a name mangling whose
purpose is to prevent accidental namespace collisions in subclasses...
Caveats of select/poll vs. epoll reactors in Twisted
...ePoll is a natural replacement for Select and Poll based networking, especially with Twisted. Which makes me paranoid, its pretty rare for a better technique or methodology not to come with a price.
...
Task vs Thread differences [duplicate]
I'm new to parallel programming. There are two classes available in .NET: Task and Thread .
4 Answers
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Clone Object without reference javascript [duplicate]
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This is really very good reply. I got the exact solution for my problem. Thanks.
– Sumit Tawal
Jul 10 '15 at 12:26
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Efficiency of Java “Double Brace Initialization”?
...2$8.class
2009/05/27 16:35 2,022 DemoApp2$9.class
These are all classes which were generated when I was making a simple application, and used copious amounts of anonymous inner classes -- each class will be compiled into a separate class file.
The "double brace initialization", as al...
How do you see recent SVN log entries?
...n the given dates:
svn log -r {2011-02-02}:{2011-02-03}
You can combine all the above expressions with the --limit option, so that can you have a quite granular control over what is printed. For more info about these -r expressions refer to svn help log or the relevant chapter in the book Version...
What is the difference between a field and a property?
...sed via get and set properties. Properties provide a level of abstraction allowing you to change the fields while not affecting the external way they are accessed by the things that use your class.
public class MyClass
{
// this is a field. It is private to your class and stores the actual da...
How can I pretty-print JSON in a shell script?
...ou can use
curl http://my_url/ | python -m json.tool
For convenience in all of these cases you can make an alias:
alias prettyjson='python -m json.tool'
For even more convenience with a bit more typing to get it ready:
prettyjson_s() {
echo "$1" | python -m json.tool
}
prettyjson_f() {...