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What is the difference between concurrency, parallelism and asynchronous methods?
Concurrency is having two tasks run in parallel on separate threads. However, asynchronous methods run in parallel but on the same 1 thread. How is this achieved? Also, what about parallelism?
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When to use Hadoop, HBase, Hive and Pig?
... too huge.
Coming back to the first part of your question, Hadoop is basically 2 things: a Distributed FileSystem (HDFS) + a Computation or Processing framework (MapReduce). Like all other FS, HDFS also provides us storage, but in a fault tolerant manner with high throughput and lower risk of data ...
Iterate through every file in one directory
...lways include . and .. (the current and parent directories). You will generally not want to work on them, so you can use Dir::each_child or Dir::children (as suggested by ma11hew28) or do something like this:
Dir.foreach('/path/to/dir') do |filename|
next if filename == '.' or filename == '..'
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jQuery: how to change title of document during .ready()?
...ards is right. It's just a method to let Google read contents that are normally generated with AJAX, via HTML snapshots and some server side modifications.
– Sk8erPeter
Jul 23 '12 at 12:52
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'IF' in 'SELECT' statement - choose output value based on column values
...tp://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html.
Additionally, you could handle when the condition is null. In the case of a null amount:
SELECT id,
IF(type = 'P', IFNULL(amount,0), IFNULL(amount,0) * -1) as amount
FROM report
The part IFNULL(amount,0) means when amount ...
MySQL - Make an existing Field Unique
...e you don't have duplicates first, no?
– William T. Mallard
Apr 16 '14 at 20:04
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Be sure to make...
Under what conditions is a JSESSIONID created?
...s created/sent when session is created. Session is created when your code calls request.getSession() or request.getSession(true) for the first time. If you just want to get the session, but not create it if it doesn't exist, use request.getSession(false) -- this will return you a session or null. In...
MySQL: Can't create table (errno: 150)
... child table InnoDB engine. Current create.sql script was using InnoDB for all tables, but I had very very old installation where first script used MyISAM.
– Whome
Apr 8 '13 at 9:50
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How do I cancel form submission in submit button onclick event?
...r jQuery) that has a good event handling API and tie into the event that really matters (i.e. the form's submit event instead of the button's click event).
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Can I grep only the first n lines of a file?
... Is there a way to do this when using grep's -l option? I'd like to list all the files who's first 5 characters are RIFFD.
– James M. Lay
May 23 '17 at 19:20
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