Обсуждение: Advisory lock grant order

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Advisory lock grant order

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Yossi Cohen

Дата:

09 сентября 2014 г., 09:44:16

Hi,

If I request an advisory lock (pg_advisory_lock) with the same key from several sessions; will the lock be granted in the same order as it was requested?

I.e. if for example:

session 1: select pg_advisory_lock(1); -- acquires the lock

then

session 2: select pg_advisory_lock(1); -- blocks waiting for the lock

then

session 3: select pg_advisory_lock(1); -- blocks waiting for the lock

then

session 1: select pg_advisory_unlock(1); -- releases the lock

Is it guaranteed that now session 2 will be granted the lock because it requested the lock before session 3?

Thanks,

Yossi

Re: Advisory lock grant order

От

Tom Lane

Дата:

09 сентября 2014 г., 13:28:20

Yossi Cohen <yossic00@gmail.com> writes:
> If I request an advisory lock (pg_advisory_lock) with the same key from
> several sessions; will the lock be granted in the same order as it was
> requested?

Usually.  IIRC, the lock code will grant locks out-of-order if a deadlock
would result without it.  There might be some other exceptions but I
don't recall any.

            regards, tom lane

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Обсуждение: Advisory lock grant order

Advisory lock grant order

Re: Advisory lock grant order