Re: User Level Lock question

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От Tom Lane
Тема Re: User Level Lock question
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Msg-id 21074.1016205095@sss.pgh.pa.us
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Ответ на User Level Lock question  ("Lance Ellinghaus" <lellinghaus@yahoo.com>)
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"Lance Ellinghaus" <lellinghaus@yahoo.com> writes:
> Is there an easy way to test the lock on a user level lock without actually
> issuing the lock?

Why would you ever want to do such a thing?  If you "test" the lock but
don't actually acquire it, someone else might acquire the lock half a
microsecond after you look at it --- and then what does your test result
mean?  It's certainly unsafe to take any action based on assuming that
the lock is free.

I suspect what you really want is a conditional acquire, which you can
get (in recent versions) using the dontWait parameter to LockAcquire.
        regards, tom lane


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