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Re: FOR UPDATE combined in a single query
Posted by: Rick James
Date: February 10, 2013 10:05AM

As far as the outside world can see, nothing happens until the COMMIT. So, does it matter? OK, maybe the TRANSACTION ISOLATION LEVEL partially controls this.

I suggest you write two PHP (or other) scripts, stick SLEEP(5) in them (certainly not more than 50 seconds), and play the scripts in "parallel". Note: In case 1, use PHP's sleep; in case 2, use MySQL's.

The TRANSACTION ISOLATION LEVEL may also factor in, so try it with different values.

There are two things to look for -- what values does the second script see, and when does the it run. This last question will answer your locking question.

Also try with/without FOR UPDATE.

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Re: FOR UPDATE combined in a single query
February 10, 2013 10:05AM


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