Improve error messages for incorrect types of logical replication targets

If trying to use something else than a plain table as logical
replication target, a rather-generic error message gets used to report
the problem.  This can be confusing when it comes to foreign tables and
partitioned tables, so use more dedicated messages in these cases.

Author: Amit Langote
Reviewed-by: Peter Eisentraut, Magnus Hagander, Michael Paquier
Discussion: https://postgr.es/m/41799bee-40eb-7bb5-80b1-325ce17518bc@lab.ntt.co.jp

Author: michaelpq

src/backend/executor/execReplication.c

@@ -609,11 +609,29 @@ CheckSubscriptionRelkind(char relkind, const char *nspname,
 						 const char *relname)
 {
 	/*
-	 * We currently only support writing to regular tables.
+	 * We currently only support writing to regular tables.  However, give
+	 * a more specific error for partitioned and foreign tables.
 	 */
+	if (relkind == RELKIND_PARTITIONED_TABLE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("cannot use relation \"%s.%s\" as logical replication target",
+						nspname, relname),
+				 errdetail("\"%s.%s\" is a partitioned table.",
+						nspname, relname)));
+	else if (relkind == RELKIND_FOREIGN_TABLE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("cannot use relation \"%s.%s\" as logical replication",
+						nspname, relname),
+				 errdetail("\"%s.%s\" is a foreign table.",
+						nspname, relname)));
+
 	if (relkind != RELKIND_RELATION)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("logical replication target relation \"%s.%s\" is not a table",
+				 errmsg("cannot use relation \"%s.%s\" as logical replication target",
+						nspname, relname),
+				 errdetail("\"%s.%s\" is not a table.",
 						nspname, relname)));
 }