Re: Column Filtering in Logical Replication

On Mon, Sep 27, 2021 at 5:53 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
>
> On 2021-Sep-27, Amit Kapila wrote:
>
> > I am not sure what makes you say that we can't distinguish the above
> > cases when there is already a separate rule for CURRENT_SCHEMA? I
> > think you can distinguish by tracking the previous objects as we are
> > already doing in the patch. But one thing that is not clear to me is
> > is the reason to introduce a new type PUBLICATIONOBJ_CURRSCHEMA when
> > we use PUBLICATIONOBJ_REL_IN_SCHEMA and PUBLICATIONOBJ_CONTINUATION to
> > distinguish all cases of CURRENT_SCHEMA. Alvaro might have something
> > in mind for this which is not apparent and that might have caused
> > confusion to you as well?
>
> My issue is what happens if you have a schema that is named
> CURRENT_SCHEMA. In the normal case where you do ALL TABLES IN SCHEMA
> "CURRENT_SCHEMA" you would end up with a String containing
> "CURRENT_SCHEMA", so how do you distinguish that from ALL TABLES IN
> SCHEMA CURRENT_SCHEMA, which does not refer to the schema named
> "CURRENT_SCHEMA" but in Vignesh's proposal also uses a String containing
> "CURRENT_SCHEMA"?
>
> Now you could say "but who would be stupid enough to do that??!",
>

But it is not allowed to create schema or table with the name
CURRENT_SCHEMA, so not sure if we need to do anything special for it.
However, if we want to handle it as a separate enum then the handling
would be something like:

| ALL TABLES IN_P SCHEMA CURRENT_SCHEMA
{
$$ =
makeNode(PublicationObjSpec);
$$->pubobjtype =
PUBLICATIONOBJ_CURRSCHEMA;
}
...
...
| CURRENT_SCHEMA
{
$$ =
makeNode(PublicationObjSpec);
$$->pubobjtype =
PUBLICATIONOBJ_CONTINUATION;
}
;

Now, during post-processing, the PUBLICATIONOBJ_CONTINUATION will be
distinguished as CURRENT_SCHEMA because both rangeVar and name will be
NULL. Do you have other ideas to deal with it? Vignesh has already
point in his email [1] why we can't keep pubobjtype as
PUBLICATIONOBJ_CURRSCHEMA in the second case, so I used
PUBLICATIONOBJ_CONTINUATION.

[1] - https://www.postgresql.org/message-id/CALDaNm06shp%2BALwC2s-dV-S4k2o6bcmXnXGX4ETkoXxKHQfjfA%40mail.gmail.com

--
With Regards,
Amit Kapila.