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When do we have to use copy constructors?
...ly, this is cached/memoized data accumulated over the object's lifetime in order to speed-up certain slow query operations performed by the object. It is safe to skip copying that data since it will be recalculated when (and if!) the relevant operations are performed. Copying this data may be unjust...
How do I delete rows in a data frame?
...ld generally avoid deleting rows by numeric position. This is because the order of the rows in your data may change in the future. A general principle of a data.frame or database tables is that the order of the rows should not matter. If the order does matter, this should be encoded in an actual va...
phpmyadmin logs out after 1440 secs
...ime by adding the following to your config.inc.php file (typically in the /etc/phpmyadmin directory): ini_set('session.gc_maxlifetime', '36000'); This will also localize it to phpmyadmin and not affect the Garbage Collection period of other PHP scripts. And, based on the documentation, the config.i...
Configure apache to listen on port other than 80
...
In /etc/apache2/ports.conf, change the port as
Listen 8079
Then go to /etc/apache2/sites-enabled/000-default.conf
And change the first line as
<VirtualHost *: 8079>
Now restart
sudo service apache2 restart
Apach...
How do I create a crontab through a script
... used to control different cron tasks (control-marker-1, control-marker-2, etc...): (crontab -l 2>/dev/null | grep -v control-marker-1; echo '*/5 * * * * /path/to/job -with args #control-marker-1') | crontab -
– chef
Dec 25 '16 at 10:39
...
Which are more performant, CTE or temporary tables?
...Example 2
WITH CTE2
AS (SELECT *,
ROW_NUMBER() OVER (ORDER BY A) AS RN
FROM T
WHERE B % 100000 = 0)
SELECT *
FROM CTE2 T1
CROSS APPLY (SELECT TOP (1) *
FROM CTE2 T2
WHERE T2.A > T1.A
...
Can you provide some examples of why it is hard to parse XML and HTML with a regex? [closed]
...HTML and XML are recursive structures which require counting mechanisms in order to properly parse. A true regex is not capable of counting. You must have a context free grammar in order to count.
The previous paragraph comes with a slight caveat. Certain regex implementations now support the ide...
Best way to do nested case statement logic in SQL Server
...1 ELSE NULL END,
CASE WHEN condition2 THEN calculation2 ELSE NULL END,
etc...
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Null coalescing in powershell
...suggestion from an anonymous user. Thanks, whoever you are!
Based on the order of operations, this works in following order:
The , operator creates an array of values to be tested.
The -ne operator filters out any items from the array that match the specified value--in this case, null. The resu...
How to retrieve an element from a set without removing it?
... since iteration seems to sort the elements. I would prefer them in random order...
– Daren Thomas
Sep 12 '08 at 20:17
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