Re: row filtering for logical replication

On Wed, Jul 14, 2021 at 6:28 AM Euler Taveira <euler(at)eulerto(dot)com> wrote:
>
> On Tue, Jul 13, 2021, at 6:06 PM, Alvaro Herrera wrote:
>
> 1. if you use REPLICA IDENTITY FULL, then the expressions would work
> even if they use any other column with DELETE. Maybe it would be
> reasonable to test for this in the code and raise an error if the
> expression requires a column that's not part of the replica identity.
> (But that could be relaxed if the publication does not publish
> updates/deletes.)
>

+1.

> I thought about it but came to the conclusion that it doesn't worth it. Even
> with REPLICA IDENTITY FULL expression evaluates to false if the column allows
> NULL values. Besides that REPLICA IDENTITY is changed via another DDL (ALTER
> TABLE) and you have to make sure you don't allow changing REPLICA IDENTITY
> because some row filter uses the column you want to remove from it.
>

Yeah, that is required but is it not feasible to do so?

> 2. For UPDATE, does the expression apply to the old tuple or to the new
> tuple? You say it's the new tuple, but from the user point of view I
> think it would make more sense that it would apply to the old tuple.
> (Of course, if you're thinking that the R.I. is the PK and the PK is
> never changed, then you don't really care which one it is, but I bet
> that some people would not like that assumption.)
>
> New tuple. The main reason is that new tuple is always there for UPDATEs.
>

I am not sure if that is a very good reason to use a new tuple.

--
With Regards,
Amit Kapila.