PostgreSQL Rule does not work with deferred constraint.

[Louis Tian <louis.tian@xxxxxxxxxxxxxxxx>]

Hi all,

Encountered a possible bug today. In short, it appears that the rule system is not deferring the constraint checking as specified. Here is an example.

create table "parent" (

  "id" uuid primary key

);

create table "children" (

  "id" uuid primary key

      default gen_random_uuid()

       references parent("id")

            deferrable

            initially deferred

);

-- this works as expected.

begin;

      insert into "children" values ('74c247be-2fc3-43e5-94f8-d5e1af147a9b');

      insert into "parent" values ('74c247be-2fc3-43e5-94f8-d5e1af147a9b');

commit;

-- doing the same with a rule

create rule on_insert as on insert to "children" do also (

      insert into "parent" (id) values (new."id");

);

-- this fails with:

--    ERROR:  insert or update on table "children" violates foreign key constraint "children_id_fkey"

--    DETAIL:  Key (id)=(40513132-f9fa-4e5a-aa46-20c8185b3e58) is not present in table "parent".

--    SQL state: 23503

insert into "children" values (default);

The rules system supposedly transforms the insert statement and executed the rule action in the same transaction. So I think it should work. 

But I got the same error on both pg13 and pg14.

Is there something I missed here? or is my understanding of the rule system just simply wrong? 

Regards,

Louis Tian

louis.tian@xxxxxxxxxxxxxxxx