RE: row filtering for logical replication

On Fri, Nov 5, 2021 4:49 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> On Fri, Nov 5, 2021 at 10:44 AM Peter Smith <smithpb2250@gmail.com> wrote:
> >
> > PSA new set of v37* patches.
> 3.
> - | ColId
> + | ColId OptWhereClause
>   {
>   $$ = makeNode(PublicationObjSpec);
>   $$->pubobjtype = PUBLICATIONOBJ_CONTINUATION;
> - $$->name = $1;
> + if ($2)
> + {
> + $$->pubtable = makeNode(PublicationTable); $$->pubtable->relation =
> + makeRangeVar(NULL, $1, @1); $$->pubtable->whereClause = $2; } else {
> + $$->name = $1; }
> 
> Again this doesn't appear to be the right way. I think this should be handled at
> a later point.

I think the difficulty to handle this at a later point is that we need to make
sure we don't lose the whereclause. Currently, we can only save the whereclause
in PublicationTable structure and the PublicationTable is only used for TABLE,
but '| ColId' can be used for either a SCHEMA or TABLE. We cannot distinguish
the actual type at this stage, so we always need to save the whereclause if
it's NOT NULL.

I think the possible approaches to delay this check are:

(1) we can delete the PublicationTable structure and put all the vars(relation,
whereclause) in PublicationObjSpec. In this approach, we don't need check if
the whereclause is NULL in the '| ColId', we can check this at a later point.

Or

(2) Add a new pattern for whereclause in PublicationObjSpec:

The change could be:

PublicationObjSpec:
...
| ColId
    ... 
+ | ColId WHERE '(' a_expr ')'
+ {
+ $$ = makeNode(PublicationObjSpec);
+ $$->pubobjtype = PUBLICATIONOBJ_CONTINUATION;
+ $$->pubtable = makeNode(PublicationTable);
+ $$->pubtable->relation = makeRangeVar(NULL, $1, @1);
+ $$->pubtable->whereClause = $2;
+ }

In this approach, we also don't need the "if ($2)" check.

What do you think ?

Best regards,
Hou zj