Band-aid fix for incorrect use of view options as StdRdOptions.

We really ought to make StdRdOptions and the other decoded forms of
reloptions self-identifying, but for the moment, assume that only plain
relations could possibly be user_catalog_tables.  Fixes problem with bogus
"ON CONFLICT is not supported on table ... used as a catalog table" error
when target is a view with cascade option.

Discussion: <26681.1477940227@sss.pgh.pa.us>

src/include/utils/rel.h

@@ -270,7 +270,8 @@ typedef struct StdRdOptions
  *		from the pov of logical decoding.  Note multiple eval of argument!
  */
 #define RelationIsUsedAsCatalogTable(relation)	\
-	((relation)->rd_options ?				\
+	((relation)->rd_rel->relkind == RELKIND_RELATION && \
+	 (relation)->rd_options ? \
 	 ((StdRdOptions *) (relation)->rd_options)->user_catalog_table : false)
 
 /*

src/test/regress/expected/insert_conflict.out

@@ -471,6 +471,30 @@ on conflict (b) where coalesce(a, 1) > 0 do nothing;
 insert into insertconflict values (1, 2)
 on conflict (b) where coalesce(a, 1) > 1 do nothing;
 drop table insertconflict;
+--
+-- test insertion through view
+--
+create table insertconflict (f1 int primary key, f2 text);
+create view insertconflictv as
+  select * from insertconflict with cascaded check option;
+insert into insertconflictv values (1,'foo')
+  on conflict (f1) do update set f2 = excluded.f2;
+select * from insertconflict;
+ f1 | f2  
+----+-----
+  1 | foo
+(1 row)
+
+insert into insertconflictv values (1,'bar')
+  on conflict (f1) do update set f2 = excluded.f2;
+select * from insertconflict;
+ f1 | f2  
+----+-----
+  1 | bar
+(1 row)
+
+drop view insertconflictv;
+drop table insertconflict;
 -- ******************************************************************
 -- *                                                                *
 -- * Test inheritance (example taken from tutorial)                 *

src/test/regress/sql/insert_conflict.sql

@@ -283,6 +283,24 @@ on conflict (b) where coalesce(a, 1) > 1 do nothing;
 
 drop table insertconflict;
 
+--
+-- test insertion through view
+--
+
+create table insertconflict (f1 int primary key, f2 text);
+create view insertconflictv as
+  select * from insertconflict with cascaded check option;
+
+insert into insertconflictv values (1,'foo')
+  on conflict (f1) do update set f2 = excluded.f2;
+select * from insertconflict;
+insert into insertconflictv values (1,'bar')
+  on conflict (f1) do update set f2 = excluded.f2;
+select * from insertconflict;
+
+drop view insertconflictv;
+drop table insertconflict;
+
 
 -- ******************************************************************
 -- *                                                                *