Re: concurrent SELECT blocking ALTER?

Note the number of exclusive locks in my first message, it is equal to the
number of threads (20). Also, the ALTER was not running then, apologies if
that was not clear.

On Wednesday, January 29, 2014, Thomas Kellerer <spam_eater(at)gmx(dot)net> wrote:

> Neil Harkins wrote on 29.01.2014 23:37:
>
>> I totally understand DDL taking exclusive locks, the problem here seems
>> to be that the *SELECTs*
>> are taking out exclusive locks, locking out the ALTER, which feels like a
>> bug.
>>
>
> The SELECT is not holding an exclusive lock, it's holing a *shared* lock,
> but the ALTER is _requesting_ an exclusive lock and that can only be
> granted until all shared (or otherwise incompatible) locks are released.
>
>
>
>
>
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