Re: Column Filtering in Logical Replication

On Fri, Sep 17, 2021 at 9:36 AM vignesh C <vignesh21@gmail.com> wrote:
>
> On Thu, Sep 16, 2021 at 7:20 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> > On 2021-Sep-16, vignesh C wrote:
> >
> > > diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
> > > index e3068a374e..c50bb570ea 100644
> > > --- a/src/backend/parser/gram.y
> > > +++ b/src/backend/parser/gram.y
> >
> > Yeah, on a quick glance this looks all wrong.  Your PublicationObjSpec
> > production should return a node with tag PublicationObjSpec, and
> > pubobj_expr should not exist at all -- that stuff is just making it all
> > more confusing.
> >
> > I think it'd be something like this:
> >
> > PublicationObjSpec:
> >                         ALL TABLES
> >                                         {
> >                                                 $$ = makeNode(PublicationObjSpec);
> >                                                 $$->pubobjtype = PUBLICATIONOBJ_ALL_TABLES;
> >                                                 $$->location = @1;
> >                                         }
> >                         | TABLE qualified_name
> >                                         {
> >                                                 $$ = makeNode(PublicationObjSpec);
> >                                                 $$->pubobjtype = PUBLICATIONOBJ_TABLE;
> >                                                 $$->pubobj = $2;
> >                                                 $$->location = @1;
> >                                         }
> >                         | ALL TABLES IN_P SCHEMA name
> >                                         {
> >                                                 $$ = makeNode(PublicationObjSpec);
> >                                                 $$->pubobjtype = PUBLICATIONOBJ_ALL_TABLES_IN_SCHEMA;
> >                                                 $$->pubobj = makeRangeVar( ... $5 ... );
> >                                                 $$->location = @1;
> >                                         }
> >                         | qualified_name
> >                                         {
> >                                                 $$ = makeNode(PublicationObjSpec);
> >                                                 $$->pubobjtype = PUBLICATIONOBJ_CONTINUATION;
> >                                                 $$->pubobj = $1;
> >                                                 $$->location = @1;
> >                                         };
> >
> > You need a single object name under TABLE, not a list -- this was Tom's
> > point about needing post-processing to determine how to assign a type to
> > a object that's what I named PUBLICATIONOBJ_CONTINUATION here.
>
> In the above, we will not be able to use qualified_name, as
> qualified_name will not support the following syntaxes:
> create publication pub1 for table t1 *;
> create publication pub1 for table ONLY t1 *;
> create publication pub1 for table ONLY (t1);
>
> To solve this problem we can change qualified_name to relation_expr
> but the problem with doing that is that the user will be able to
> provide the following syntaxes:
> create publication pub1 for all tables in schema sch1 *;
> create publication pub1 for all tables in schema ONLY sch1 *;
> create publication pub1 for all tables in schema ONLY (sch1);
>
> To handle this we will need some special flag which will differentiate
> these and throw errors at post processing time. We need to define an
> expression similar to relation_expr say pub_expr which handles all
> variants of qualified_name and then use a special flag so that we can
> throw an error if somebody uses the above type of syntax for schema
> names. And then if we have to distinguish between schema name and
> relation name variant, then we need few other things.
>
> We proposed the below solution which handles all these problems and
> also used Node type which need not store schemaname in RangeVar type:
>

Alvaro, do you have any thoughts on these proposed grammar changes?

-- 
With Regards,
Amit Kapila.