Re: Pgoutput not capturing the generated columns - Mailing list pgsql-hackers

On Wed, 16 Oct 2024 at 23:25, Shubham Khanna
<khannashubham1197@gmail.com> wrote:
>
> On Wed, Oct 9, 2024 at 9:08 AM vignesh C <vignesh21@gmail.com> wrote:
> >
> > On Tue, 8 Oct 2024 at 11:37, Shubham Khanna <khannashubham1197@gmail.com> wrote:
> > >
> > > On Fri, Oct 4, 2024 at 9:36 AM Peter Smith <smithpb2250@gmail.com> wrote:
> > > >
> > > > Hi Shubham, here are my review comments for v36-0001.
> > > >
> > > > ======
> > > > 1. General  - merge patches
> > > >
> > > > It is long past due when patches 0001 and 0002 should've been merged.
> > > > AFAIK the split was only because historically these parts had
> > > > different authors. But, keeping them separated is not helpful anymore.
> > > >
> > > > ======
> > > > src/backend/catalog/pg_publication.c
> > > >
> > > > 2.
> > > >  Bitmapset *
> > > > -pub_collist_validate(Relation targetrel, List *columns)
> > > > +pub_collist_validate(Relation targetrel, List *columns, bool pubgencols)
> > > >
> > > > Since you removed the WARNING, this parameter 'pubgencols' is unused
> > > > so it should also be removed.
> > > >
> > > > ======
> > > > src/backend/replication/pgoutput/pgoutput.c
> > > >
> > > > 3.
> > > >   /*
> > > > - * If the publication is FOR ALL TABLES then it is treated the same as
> > > > - * if there are no column lists (even if other publications have a
> > > > - * list).
> > > > + * To handle cases where the publish_generated_columns option isn't
> > > > + * specified for all tables in a publication, we must create a column
> > > > + * list that excludes generated columns. So, the publisher will not
> > > > + * replicate the generated columns.
> > > >   */
> > > > - if (!pub->alltables)
> > > > + if (!(pub->alltables && pub->pubgencols))
> > > >
> > > > I still found that comment hard to understand. Does this mean to say
> > > > something like:
> > > >
> > > > ------
> > > > Process potential column lists for the following cases:
> > > >
> > > > a. Any publication that is not FOR ALL TABLES.
> > > >
> > > > b. When the publication is FOR ALL TABLES and
> > > > 'publish_generated_columns' is false.
> > > > A FOR ALL TABLES publication doesn't have user-defined column lists,
> > > > so all columns will be replicated by default. However, if
> > > > 'publish_generated_columns' is set to false, column lists must still
> > > > be created to exclude any generated columns from being published
> > > > ------
> > > >
> > > > ======
> > > > src/test/regress/sql/publication.sql
> > > >
> > > > 4.
> > > > +SET client_min_messages = 'WARNING';
> > > > +CREATE TABLE gencols (a int, gen1 int GENERATED ALWAYS AS (a * 2) STORED);
> > > >
> > > > AFAIK you don't need to keep changing 'client_min_messages',
> > > > particularly now that you've removed the WARNING message that was
> > > > previously emitted.
> > > >
> > > > ~
> > > >
> > > > 5.
> > > > nit - minor comment changes.
> > > >
> > > > ======
> > > > Please refer to the attachment which implements any nits from above.
> > > >
> > >
> > > I have fixed all the given comments. Also, I have created a new 0003
> > > patch for the TAP-Tests related to the '011_generated.pl' file. I am
> > > planning to merge 0001 and 0003 patches once they will get fixed.
> > > The attached patches contain the required changes.
> >
> > Few comments:
> > 1) Since we are no longer throwing an error for generated columns, the
> > function header comments also need to be updated accordingly " Checks
> > for and raises an ERROR for any; unknown columns, system columns,
> > duplicate columns or generated columns."
> > -               if (TupleDescAttr(tupdesc, attnum - 1)->attgenerated)
> > -                       ereport(ERROR,
> > -
> > errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
> > -                                       errmsg("cannot use generated
> > column \"%s\" in publication column list",
> > -                                                  colname));
> > -
> >
> > 2) Tab completion missing for "PUBLISH_GENERATED_COLUMNS" option in
> > ALTER PUBLICATION ... SET (
> > postgres=# alter publication pub2 set (PUBLISH
> > PUBLISH                     PUBLISH_VIA_PARTITION_ROOT
> >
> > 3) I was able to compile without this include, may be this is not required:
> > --- a/src/backend/replication/logical/tablesync.c
> > +++ b/src/backend/replication/logical/tablesync.c
> > @@ -118,6 +118,7 @@
> >  #include "utils/builtins.h"
> >  #include "utils/lsyscache.h"
> >  #include "utils/memutils.h"
> > +#include "utils/rel.h"
> >
> > 4) You can include "\dRp+ pubname" after each of the create/alter
> > publication to verify the columns that will be published:
> > +-- Test the 'publish_generated_columns' parameter enabled or disabled for
> > +-- different scenarios with/without generated columns in column lists.
> > +CREATE TABLE gencols (a int, gen1 int GENERATED ALWAYS AS (a * 2) STORED);
> > +
> > +-- Generated columns in column list, when 'publish_generated_columns'=false
> > +CREATE PUBLICATION pub1 FOR table gencols(a, gen1) WITH
> > (publish_generated_columns=false);
> >
> > +-- Generated columns in column list, when 'publish_generated_columns'=true
> > +CREATE PUBLICATION pub2 FOR table gencols(a, gen1) WITH
> > (publish_generated_columns=true);
> > +
> > +-- Generated columns in column list, then set
> > 'publication_generate_columns'=false
> > +ALTER PUBLICATION pub2 SET (publish_generated_columns = false);
> > +
> > +-- Remove generate columns from column list, when
> > 'publish_generated_columns'=false
> > +ALTER PUBLICATION pub2 SET TABLE gencols(a);
> > +
> > +-- Add generated columns in column list, when 'publish_generated_columns'=false
> > +ALTER PUBLICATION pub2 SET TABLE gencols(a, gen1);
> >
>
> I have fixed all the given comments. The attached patches contain the
> required changes.

Few comments:
1) This change is not required:
diff --git a/src/backend/catalog/pg_subscription.c
b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..fcfbf86c0b 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -551,3 +551,34 @@ GetSubscriptionRelations(Oid subid, bool not_ready)

        return res;
 }
+
+/*
+ * Add publication names from the list to a string.
+ */
+void
+get_publications_str(List *publications, StringInfo dest, bool quote_literal)
+{
+       ListCell   *lc;
+       bool            first = true;
+
+       Assert(publications != NIL);
+
+       foreach(lc, publications)
+       {
+               char       *pubname = strVal(lfirst(lc));
+
+               if (first)
+                       first = false;
+               else
+                       appendStringInfoString(dest, ", ");
+
+               if (quote_literal)
+                       appendStringInfoString(dest,
quote_literal_cstr(pubname));
+               else
+               {
+                       appendStringInfoChar(dest, '"');
+                       appendStringInfoString(dest, pubname);
+                       appendStringInfoChar(dest, '"');
+               }
+       }
+}

It can be moved to subscriptioncmds.c file as earlier.

2) This line change is not required:
  *             Process and validate the 'columns' list and ensure the
columns are all
- *             valid to use for a publication.  Checks for and raises
an ERROR for
- *             any; unknown columns, system columns, duplicate
columns or generated
- *             columns.
+ *             valid to use for a publication. Checks for and raises
an ERROR for

3) Can we store this information in LogicalRepRelation instead of
having a local variable as column information is being stored, that
way remotegenlist and remotegenlist_res can be removed and code will
be more simpler:
+               if (server_version >= 180000)
+               {
+                       remotegenlist[natt] =
DatumGetBool(slot_getattr(slot, 5, &isnull));
+
+                       /*
+                        * If the column is generated and neither the
generated column
+                        * option is specified nor it appears in the
column list, we will
+                        * skip it.
+                        */
+                       if (remotegenlist[natt] &&
!has_pub_with_pubgencols && !included_cols)
+                       {
+                               ExecClearTuple(slot);
+                               continue;
+                       }
+               }
+
                rel_colname = TextDatumGetCString(slot_getattr(slot,
2, &isnull));
                Assert(!isnull);

@@ -1015,7 +1112,7 @@ fetch_remote_table_info(char *nspname, char *relname,
        ExecDropSingleTupleTableSlot(slot);

        lrel->natts = natt;
-
+       *remotegenlist_res = remotegenlist;

Regards,
Vignesh