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When and why are database joins expensive?
...ically demolished them using scientific method: he got large databases and tested these assertions.
I think he wrote it up in Relational Database Writings 1988-1991 but this book was later rolled into edition six of Introduction to Database Systems, which is the definitive text on database theory ...
Generating v5 UUID. What is name and namespace?
...id = NameToUUID(Namespace_URL, 'http://stackoverflow.com/questions/5515880/test-vectors-for-uuid-version-5-converting-hash-into-guid-algorithm');
Now back to your question
For version 3 and version 5 UUIDs the additional command line arguments namespace and name have to be given. The namespace is ...
Prototypical inheritance - writing up [duplicate]
...
It's good because it enables you and others to mock certain members for testing easily. It gives others a chance to easily improve (patch) your code but this is also bad because there is no guarantee that a next version of your code has the same implementation and or private members.
By using cl...
Why does GCC generate such radically different assembly for nearly the same C code?
...
This is the nature of compilers. Assuming they will take the fastest or best path, is quite false. Anyone that implies that you don't need to do anything to your code to optimize because "modern compilers" fill in the blank, do the best job, make the fastest code, etc. Actually I saw gc...
What Every Programmer Should Know About Memory?
...ops when it's worth have a look at the compiler's asm output: C++ code for testing the Collatz conjecture faster than hand-written asm?
– Peter Cordes
Apr 9 '19 at 7:31
add a ...
Is Java really slow?
...
Modern Java is one of the fastest languages, even though it is still a memory hog. Java had a reputation for being slow because it used to take a long time for the VM to start up.
If you still think Java is slow, see the benchmarks game results. Tightl...
Why does NULL = NULL evaluate to false in SQL server
...f NULL you think of “NULL” (string) then you probably want a different test of equality like Postgresql's IS DISTINCT FROM AND IS NOT DISTINCT FROM
From the PostgreSQL docs on "Comparison Functions and Operators"
expression IS DISTINCT FROM expression
expression IS NOT DISTINCT FROM expression
...
Draw a perfect circle from user's touch
...ased on that idea. See working demo below (Sorry, I'm using Java as the fastest way to provide this fast and a bit dirty example):
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.HeadlessException;
...
Why would you use an ivar?
... CFAbsoluteTimeGetCurrent();
for (unsigned i = 0; i < kRuns; i++) {
testIVar = i;
}
cft = CFAbsoluteTimeGetCurrent() - cft;
NSLog(@"1: %.1f picoseconds/run", (cft * 10000000000.0) / kRuns);
cft = CFAbsoluteTimeGetCurrent();
for (unsigned i = 0; i < kRuns; i++) {
[self setTestIVar:i];
...
正则表达式 30 分钟入门教程 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...请参考该页面的说明来安装和运行该软件。
下面是Regex Tester运行时的截图：
元字符
现在你已经知道几个很有用的元字符了，如\b,.,*，还有\d.正则表达式里还有更多的元字符，比如\s匹配任意的空白符，包括空格，制表符(Tab)...