Re: Online enabling of checksums

On Thu, Feb 22, 2018 at 8:52 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:

>
>
> On February 22, 2018 11:44:17 AM PST, Magnus Hagander <magnus(at)hagander(dot)net>
> wrote:
> >On Thu, Feb 22, 2018 at 8:41 PM, Andres Freund <andres(at)anarazel(dot)de>
> >wrote:
> >In this particular case that would at least phase 1 simplify it because
> >we'd only need one process instead of worker/launcher. However, if we'd
> >ever want to parallellize it -- or any other process of the style, like
> >autovacuum -- you'd still need a launcher+worker combo. So making that
> >particular scenario simpler might be worthwhile on it's own.
>
> Why is that needed? You can just start two bgworkers and process a list of
> items stored in shared memory. Or even just check, I assume there'd be a
> catalog flag somewhere, whether a database / table / object of granularity
> has already been processed and use locking to prevent concurrent access.
>

You could do that, but then you've moving the complexity to managing that
list in shared memory instead. I'm not sure that's any easier... And
certainly adding a catalog flag for a usecase like this one is not making
it easier.

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>