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How to free memory in Java?
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Java uses managed memory, so the only way you can allocate memory is by using the new operator, and the only way you can deallocate memory is by relying on the garbage collector.
This memory management whitepaper (PDF) may help explain what's going on.
You can also call System.gc() to sugges...
How to drop a PostgreSQL database if there are active connections to it?
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Actually it would disconnect clients one by one, and if you client is in the middle of the list it will be disconnected too. As a result, some connections will stay alive. So, the right answer is by Craig Ringer (see below). SELECT pg_terminate_backend(pg_stat_activ...
What is the purpose of the HTML “no-js” class?
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The no-js class is used by the Modernizr feature detection library. When Modernizr loads, it replaces no-js with js. If JavaScript is disabled, the class remains. This allows you to write CSS which easily targets either condition.
From Modernizrs'...
SQL: How to get the count of each distinct value in a column?
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SELECT
category,
COUNT(*) AS `num`
FROM
posts
GROUP BY
category
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How to “set a breakpoint in malloc_error_break to debug”
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Set a breakpoint on malloc_error_break() by opening the Breakpoint Navigator (View->Navigators->Show Breakpoint Navigator or ⌘8), clicking the plus button in the lower left corner, and selecting "Add Symbolic Breakpoint". In the popup that comes up, enter ma...
Django filter queryset __in for *every* item in list
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Summary:
One option is, as suggested by jpic and sgallen in the comments, to add .filter() for each category. Each additional filter adds more joins, which should not be a problem for small set of categories.
There is the aggregation approach. This query would ...
When and why I should use session_regenerate_id()?
...rability in a system to fixate (set) the session ID (SID) of another user. By doing so, they will get complete access as the original user and be able to do tasks that would otherwise require authentication.
To prevent such attacks, assign the user a new session ID using session_regenerate_id() when...
Django filter versus get for single object?
...ango.db.models.query.QuerySet.first
Returns the first object matched by the queryset, or None if there is no matching object. If the QuerySet has no ordering defined, then the queryset is automatically ordered by the primary key.
Example:
p = Article.objects.order_by('title', 'pub_date').fi...
How to change the button text of ?
... the same row) while clicking on an image! :/
– sohaiby
May 11 '15 at 12:09
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Checking network connection
...is not working, you can find a current IP address for google.com (on unix) by running
% dig google.com +trace
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google.com. 300 IN A 216.58.192.142
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