Re: Compress ReorderBuffer spill files using LZ4

Le lun. 15 juil. 2024 à 12:28, Tomas Vondra
<tomas.vondra@enterprisedb.com> a écrit :
>
> On 7/15/24 20:50, Julien Tachoires wrote:
> > The last patch of this set is still in WIP, it adds the machinery
> > required for setting the compression methods as a subscription option:
> > CREATE SUBSCRIPTION ... WITH (spill_compression = ...);
> > I think there is a major problem with this approach: the logical
> > decoding context is tied to one replication slot, but multiple
> > subscriptions can use the same replication slot. How should this work
> > if 2 subscriptions want to use the same replication slot but different
> > compression methods?
> >
>
> Do we really support multiple subscriptions sharing the same slot? I
> don't think we do, but maybe I'm missing something.

You are right, it's not supported, the following error is raised in this case:
ERROR:  replication slot "sub1" is active for PID 51735

I was distracted by the fact that nothing prevents the configuration
of multiple subscriptions sharing the same replication slot.

Thanks,

JT