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Spinlock versus Semaphore
...k is one possible implementation of a lock, namely one that is implemented by busy waiting ("spinning"). A semaphore is a generalization of a lock (or, the other way around, a lock is a special case of a semaphore). Usually, but not necessarily, spinlocks are only valid within one process whereas se...
What would cause an algorithm to have O(log log n) complexity?
... are typically two main routes that will arrive at this runtime.
Shrinking by a Square Root
As mentioned in the answer to the linked question, a common way for an algorithm to have time complexity O(log n) is for that algorithm to work by repeatedly cut the size of the input down by some constant fa...
T-SQL: Deleting all duplicate rows but keeping one [duplicate]
...is:
WITH cte AS (
SELECT[foo], [bar],
row_number() OVER(PARTITION BY foo, bar ORDER BY baz) AS [rn]
FROM TABLE
)
DELETE cte WHERE [rn] > 1
Play around with it and see what you get.
(Edit: In an attempt to be helpful, someone edited the ORDER BY clause within the CTE. To be clear, yo...
What is an EJB, and what does it do?
...r ensures that EJB instances are automatically accessed safely (serially)
by multiple clients. The container manages the EJB pool, the thread pool, the
invocation queue, and automatically carries out method-level write locking (default) or
read locking (through @Lock(READ)). This protects data ...
How to get size of mysql database?
...) / 1024 / 1024, 1) "DB Size in MB"
FROM information_schema.tables
GROUP BY table_schema;
This query comes from the mysql forums, where there are more comprehensive instructions available.
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Can't start site in IIS (use by another process)
... you need to go on the Details tab to search for the PID. Or, as mentioned by @Nikita G in the comments, you can use this command to find the task from your command prompt:
tasklist /FI "PID eq 123"
Note: change 123 with the PID returned from the first command.
...
C# Interfaces. Implicit implementation versus Explicit implementation
...mentation allows you to access the interface through the class you created by casting the interface as that class and as the interface itself. Explicit implementation allows you to access the interface only by casting it as the interface itself.
MyClass myClass = new MyClass(); // Declared as concr...
What are queues in jQuery?
... They are First-In-First-Out (FIFO). You can add a function to the queue by calling .queue(), and you remove (by calling) the functions using .dequeue().
To understand the internal jQuery queue functions, reading the source and looking at examples helps me out tremendously. One of the best examp...
MySQL load NULL values from CSV data
...at can contain from 3 to 4 columns of numerical values which are separated by comma. Empty fields are defined with the exception when they are at the end of the row:
...
How to delete from select in MySQL?
...posts WHERE id IN (
SELECT * FROM (
SELECT id FROM posts GROUP BY id HAVING ( COUNT(id) > 1 )
) AS p
)
Or use joins as suggested by Mchl.
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