Re: row filtering for logical replication

On 2021-Jul-14, Tomas Vondra wrote:

> On 7/14/21 4:52 PM, Alvaro Herrera wrote:

> > In any case, it seems to me that the condition expression should be
> > scanned to see which columns are used in Vars (pull_varattnos?), and
> > verify if those columns are in the REPLICA IDENTITY; and if they are
> > not, raise an error. Most of the time the REPLICA IDENTITY is going to
> > be the primary key; but if the user wants to use other columns in the
> > expression, we can HINT that they can set REPLICA IDENTITY FULL.
>
> Yeah, but AFAIK that's needed only when replicating DELETEs, so perhaps we
> could ignore this for subscriptions without DELETE.

Yeah, I said that too in my older reply :-)

> The other question is when to check/enforce this. I guess we'll have to do
> that during decoding, not just when the publication is being created,
> because the user can do ALTER TABLE later.

... if you're saying the user can change the replica identity after we
have some publications with filters defined, then I think we should
verify during ALTER TABLE and not allow the change if there's a
publication that requires it. I mean, during decoding we should be able
to simply assume that the tuple is correct for what we need at that
point.

--
Álvaro Herrera Valdivia, Chile — https://www.EnterpriseDB.com/