Re: group locking: incomplete patch, just for discussion

On Thu, Nov 20, 2014 at 4:21 AM, Jeff Davis <pgsql@j-davis.com> wrote:
>>   The
>> bad news, to borrow a phrase from Peter Geoghegan, is that it's an
>> unprincipled deadlock; a user confronted with the news that her
>> parallel scan has self-deadlocked will be justifiably dismayed.
>
> You seem to be raising this as a show-stopping problem, and I'm not
> convinced that it is.

Well, what I'm saying is that at very minimum we have to be able
detect deadlocks, and we have two plausible designs for avoiding that:

1. Modify the deadlock detector to know about lock groups.

2. Propagate pre-existing locks from the user backend to all the workers.

I initially proposed #1, but now I think #2 solves more of the
problems for less code.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company