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postgresql COUNT(DISTINCT …) very slow
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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)
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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'...
Can an enum class be converted to the underlying type?
...t16_t /*v*/) {
std::cout << "uint16_t!\n";
}
int main(int argc, char* argv[]) {
SomeEnum e = B;
write(util::underlying_cast(e));
return 0;
}
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Can a JSON value contain a multiline string
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Check out the specification! The JSON grammar's char production can take the following values:
any-Unicode-character-except-"-or-\-or-control-character
\"
\\
\/
\b
\f
\n
\r
\t
\u four-hex-digits
Newlines are "control characters" so, no, you may not have a literal newli...
How to enable MySQL Query Log?
...global general_log = 1;
SET global log_output = 'table';
View the log
select * from mysql.general_log;
Disable Query logging on the database
SET global general_log = 0;
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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, ...
How do I hotkey directly to File Search tab in Eclipse
... box. (If there are no results, and you have a really old Eclipse version, select the Include Unbound Commands check box.)
Put the caret into the Binding text box and press the key combination you want to use:
You can either re-use the CTRL+H binding (delete the other binding in that case) or de...
How to use PrimeFaces p:fileUpload? Listener method is never invoked or UploadedFile is null / throw
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Looks like javax.faces.SEPARATOR_CHAR must not be equal to _
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What is the effect of encoding an image in base64?
...e64 is the better choice.
Size of base64-images
Base64 uses 64 different characters and this is 2^6. So base64 stores 6bit per 8bit character. So the proportion is 6/8 from unconverted data to base64 data. This is no exact calculation, but a rough estimate.
Example:
An 48kb image needs around 64...
How to sum up an array of integers in C#
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Point taken. Yet, the following saves 18 chars compared to your sample: foreach (int i in arr) sum += i;
– Jørn Schou-Rode
Mar 16 '10 at 11:44
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