Re: Column Filtering in Logical Replication

On Thu, Sep 16, 2021 at 8:45 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Sep 15, 2021 at 6:06 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> > On 2021-Sep-15, vignesh C wrote:
> > > The patch
> > > Generic_object_type_parser_002_table_schema_publication.patch has the
> > > changes that were used to handle the parsing. Schema and Relation both
> > > are different objects, schema is of string type and relation is of
> > > RangeVar type. While parsing, schema name is parsed in string format
> > > and relation is parsed and converted to rangevar type, these objects
> > > will be then handled accordingly during post processing.
> >
> > Yeah, I think it'd be cleaner if the node type has two members, something like
> > this
> >
> > typedef struct PublicationObjSpec
> > {
> >         NodeTag         type;
> >         PublicationObjSpecType pubobjtype;      /* type of this publication object */
> >         RangeVar        *rv;            /* if a table */
> >         String          *objname;       /* if a schema */
> >         int             location;               /* token location, or -1 if unknown */
> > } PublicationObjSpec;
> >
> > and only one of them is set, the other is NULL, depending on the object type.
> >
>
> I think the problem here is that with the proposed grammar we won't be
> always able to distinguish names at the gram.y stage.

This is the issue that Amit was talking about:
gram.y: error: shift/reduce conflicts: 2 found, 0 expected
gram.y: warning: shift/reduce conflict on token ',' [-Wcounterexamples]
  First example: CREATE PUBLICATION name FOR TABLE relation_expr_list
• ',' relation_expr ',' PublicationObjSpec opt_definition $end
  Shift derivation
    $accept
    ↳ parse_toplevel
                                                              $end
      ↳ stmtmulti
        ↳ toplevel_stmt
          ↳ stmt
            ↳ CreatePublicationStmt
              ↳ CREATE PUBLICATION name FOR pub_obj_list
                                               opt_definition
                                            ↳ PublicationObjSpec
                        ',' PublicationObjSpec
                                              ↳ TABLE relation_expr_list
                                                      ↳
relation_expr_list • ',' relation_expr
  Second example: CREATE PUBLICATION name FOR TABLE relation_expr_list
• ',' PublicationObjSpec opt_definition $end
  Reduce derivation
    $accept
    ↳ parse_toplevel
                                            $end
      ↳ stmtmulti
        ↳ toplevel_stmt
          ↳ stmt
            ↳ CreatePublicationStmt
              ↳ CREATE PUBLICATION name FOR pub_obj_list
                             opt_definition
                                            ↳ pub_obj_list
      ',' PublicationObjSpec
                                              ↳ PublicationObjSpec
                                                ↳ TABLE relation_expr_list •
Here it is not able to distinguish if ',' is used for the next table
name or the next object.
I was able to reproduce this issue with the attached patch.

Regards,
Vignesh