大约有 44,000 项符合查询结果（耗时：0.0557秒） [XML]
postgresql COUNT(DISTINCT …) very slow
...
You can use this:
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
This is much faster than:
COUNT(DISTINCT column_name)
share
...
What is the HTML tabindex attribute?
...ments support the tabindex attribute: anchor, area, button, input, object, select, and textarea. But the HTML5 spec, with accessibility in mind, allows all elements to be assigned tabindex.
--
For example
<ul tabindex="-1">
<li tabindex="1"></li>
<li tabindex="2"><...
Sort a list from another list IDs
...; source,
IEnumerable<TId> order,
Func<T, TId> idSelector)
{
var lookup = source.ToDictionary(idSelector, t => t);
foreach (var id in order)
{
yield return lookup[id];
}
}
Is a generic extension for what you want.
You could use the extension li...
How do I reverse a C++ vector?
...am>
template<class InIt>
void print_range(InIt first, InIt last, char const* delim = "\n"){
--last;
for(; first != last; ++first){
std::cout << *first << delim;
}
std::cout << *first;
}
int main(){
int a[] = { 1, 2, 3, 4, 5 };
std::vector<int> v(a, ...
Capybara Ambiguity Resolution
...t
So it's adviced to choose another, less ambiguous locator: for example select element by id, class or other css/xpath locator so that only one element will match it.
As a note here are some locators that I usually consider useful when resolving ambiguity:
find('ul > li:first-child')
It'...
Failure [INSTALL_FAILED_ALREADY_EXISTS] when I tried to update my application
...lease variant
Bonus
I set up an alias in my ~/.bash_profile, to make it a 2char command.
alias bi="gradlew && adb install -r exampleApp.apk"
(Short for Build and Install)
share
|
improve th...
If table exists drop table then create it, if it does not exist just create it
...up the old table,
obviously.
Wrapping all statements with something like SELECT GET_LOCK('__upgrade', -1); ... DO RELEASE_LOCK('__upgrade'); allows to just invoke all statements sequentially without error checking, but I don't think it's a good idea: complexity increases and locking functions in M...
Default implementation for Object.GetHashCode()
...sually more interested in whether a string containing the same sequence of characters has already been added. That's why string overrides GetHashCode. On the other hand, suppose you want to keep a count of how many times various controls process Paint events. You could use a Dictionary<Object,...
Is Java really slow?
... to a self-fulfilling prophecy -- when people care about speed, they often select C++ because it has that reputation. They put extra time and effort into optimization, and a new generation of fast C++ code is written.
To summarize, the normal implementation of Java makes maximum optimization proble...
Use gulp to select and move directories and their files
... },
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true,enableSnippets:true
});
}
});
...