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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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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...
What's the difference between session.persist() and session.save() in Hibernate?
...st(entity);
session.getTransaction().commit();
session.close();
Result:
select nextval ('hibernate_sequence') // This is for vehicle Id generated : 36
insert into Employee_Vehicle ( Vehicle_Name, Vehicle_Id) values ( Honda, 36)
Note the result is same when you get an already persisted object an...
Why “no projects found to import”?
...ing to "import existing project into workspace". As the "root directory" I select the directory where all my .java (and .class) files are located. Eclipse writes me that "no projects are found to import". Why?
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How can I change an element's text without changing its child elements?
...to_change.nodeValue = 'new text';
Of course, you can still use jQuery to select the <div> in the first place (i.e. var your_div = $('your_div').get(0);).
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Facebook API “This app is in development mode”
...s%3A%2F%2Fdevelopers.facebook.com%2Fdocs%2Ffacebook-login%2Fios
STEP 2
Select your application
STEP 3
Click the app Review tab.
Change switch value no to yes. See picture below.
After this your app is live.
sha...
What is the meaning of the term arena in relation to memory?
... manage memory manually by handing out parts of that memory. For example:
char * arena = malloc(HUGE_NUMBER);
unsigned int current = 0;
void * my_malloc(size_t n) { current += n; return arena + current - n; }
The point is that you get full control over how the memory allocation works. The only ...
Input placeholders for Internet Explorer
...n(){
if (input.val() === text) input.css({ color:'lightGrey' }).selectRange(0,0).one('keydown', function(){
input.val("").css({ color:'black' });
});
});
input.blur(function(){
if (input.val() == "" || input.val() === text) input.val(text)...
Algorithm to find top 10 search terms
...sume only 300MB memory for 4 million different words. Some hint: use ASCII char to represent Strings), and this is much acceptable.
Meanwhile, there will be another process that is activated once it finds any disk file generated by the system, then start merging it. Since the disk file is sorted, m...
What exactly does stringstream do?
... answered Dec 15 '13 at 13:28
richard.grichard.g
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