>> In order to encounter this issue, I'd need to have two concurrent
>> processes update the child records of the same parent record?  That is:
>> A ---> B1
>>   \---> B2
>> ... and the issue should only happen if I update both B1 and B2
>> concurrently in separate sessions?
> I don't think that'll trigger it. You need rows that are first key share
> locked and then updated by the locking transaction. Under
> concurrency. And the timewindow really is rather small..

Well, currently I have a test which locks A and B1, then updates B1
(twice, actually), and then updates A.  However, since there's a lock on
A, there's no concurrent updating of B1 and B2. This is based on the
behavior of the queue where I originally saw the problem, but it doesn't
reproduce the bug.

I'm thinking I need to just lock B1, update B1, then A, while allowing a
concurrent session to update B2 and and A.  No?

Josh Berkus
PostgreSQL Experts Inc.

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