Re: "Multiple table synchronizations are processed serially" still happens

Le ven. 21 mai 2021 à 05:43, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> a écrit :

> On Fri, May 21, 2021 at 1:30 AM Guillaume Lelarge
> <guillaume(at)lelarge(dot)info> wrote:
> >
> >
> >> If so, the
> >> problem might be that copying the data of the first table creates a
> >> transaction which blocks creation of the slot for second table copy.
> >
> >
> > I don't understand how a transaction could block the creation of a slot.
> Could you explain that to me?
> >
>
> During the creation of the slot

During the creation of the slot or during the creation of the subscription?
because, in my tests, I create the slot before creating the snapshot.

> , we need to build the initial snapshot
> which is used for decoding WAL. Now, to build the initial snapshot, we
> wait for all running xacts to finish. See functions
> CreateReplicationSlot() and SnapBuildFindSnapshot().
>
>
If we have two workers, both will have a snapshot? they don't share the
same snapshot?

And if all this is true, I don't see how it could work when the replication
happens between two clusters, and couldn't work when it happens with only
one cluster.

--
Guillaume.