RE: Data is copied twice when specifying both child and parent table in publication - Mailing list pgsql-hackers

On Wednesday, May 11, 2022 11:33 AM I wrote:
> On Monday, May 9, 2022 10:51 AM wangw.fnst@fujitsu.com
> <wangw.fnst@fujitsu.com> wrote:
> > Attach new patches.
> > The patch for HEAD:
> > 1. Modify the approach. Enhance the API of function
> > pg_get_publication_tables to handle one publication or an array of
> > publications.
> > The patch for REL14:
> > 1. Improve the table sync SQL. [suggestions by Shi yu]
> Hi, thank you for updating the patch !
> 
> Minor comments on your patch for HEAD v2.
> 
> (1) commit message sentence
> 
> I suggest below sentence.
> 
> Kindly change from
> "... when subscribing to both publications using one subscription, the data is
> replicated twice in inital copy"
> to "subscribing to both publications from one subscription causes initial copy
> twice".
> 
> (2) unused variable
> 
> pg_publication.c: In function ‘pg_get_publication_tables’:
> pg_publication.c:1091:11: warning: unused variable ‘pubname’
> [-Wunused-variable]
>   char    *pubname;
> 
> We can remove this.
> 
> (3) free of allocated memory
> 
> In the pg_get_publication_tables(),
> we don't free 'elems'. Don't we need it ?
> 
> (4) some coding alignments
> 
> 4-1.
> 
> +       List       *tables_viaroot = NIL,
> ...
> +                          *current_table = NIL;
> 
> I suggest we can put some variables
> into the condition for the first time call of this function, like tables_viaroot and
> current_table.
> When you agree, kindly change it.
> 
> 4-2.
> 
> +                       /*
> +                        * Publications support partitioned tables, although
> all changes
> +                        * are replicated using leaf partition identity and
> schema, so we
> +                        * only need those.
> +                        */
> +                       if (publication->alltables)
> +                       {
> +                               current_table =
> GetAllTablesPublicationRelations(publication->pubviaroot);
> +                       }
> 
> This is not related to the change itself and now we are inheriting the previous
> curly brackets, but I think there's no harm in removing it, since it's only for one
> statement.
Hi, 

One more thing I'd like to add is that
we don't hit the below code by tests.
In the HEAD v2, we add a new filtering logic in pg_get_publication_tables.
Although I'm not sure if this is related to the bug fix itself,
when we want to include it in this patch, then
I feel it's better to add some simple test for this part,
to cover all the new main paths and check if
new logic works correctly.


+               /*
+                * If a partition table is published in a publication with viaroot,
+                * and its parent or child table is published in another publication
+                * without viaroot. Then we need to move the parent or child table
+                * from tables to tables_viaroot.
+                *
+                * If all publication(s)'s viaroot are the same, then skip this part.
+                */

....
                                       if (ancestor_viaroot == ancestor)
+                                       {
+                                               tables = foreach_delete_current(tables, lc2);
+                                               change_tables = list_append_unique_oid(change_tables,
+
  relid);
 
+                                       }


Best Regards,
    Takamichi Osumi