RE: bogus: logical replication rows/cols combinations

On Tuesday, May 3, 2022 11:31 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, May 3, 2022 at 12:10 AM Tomas Vondra
> <tomas(dot)vondra(at)enterprisedb(dot)com> wrote:
> >
> > On 5/2/22 19:51, Alvaro Herrera wrote:
> > >> Why would we need to know publications replicated by other
> walsenders?
> > >> And what if the subscriber is not connected at the moment? In that case
> > >> there'll be no walsender.
> > >
> > > Sure, if the replica is not connected then there's no issue -- as you
> > > say, that replica will fail at START_REPLICATION time.
> > >
> >
> > Right, I got confused a bit.
> >
> > Anyway, I think the main challenge is defining what exactly we want to
> > check, in order to ensure "sensible" behavior, without preventing way
> > too many sensible use cases.
> >
>
> I could think of below two options:
> 1. Forbid any case where column list is different for the same table
> when combining publications.
> 2. Forbid if the column list and row filters for a table are different
> in the set of publications we are planning to combine. This means we
> will allow combining column lists when row filters are not present or
> when column list is the same (we don't get anything additional by
> combining but the idea is we won't forbid such cases) and row filters
> are different.
>
> Now, I think the points in favor of (1) are that the main purpose of
> introducing a column list are: (a) the structure/schema of the
> subscriber is different from the publisher, (b) want to hide sensitive
> columns data. In both cases, it should be fine if we follow (1) and
> from Peter E.'s latest email [1] he also seems to be indicating the
> same. If we want to be slightly more relaxed then we can probably (2).
> We can decide on something else as well but I feel it should be such
> that it is easy to explain.

I also think it makes sense to add a restriction like (1). I am planning to
implement the restriction if no one objects.

Best regards,
Hou zj