Re: Forward declaration of table - Mailing list pgsql-general

On 08/23/2016 10:29 AM, David G. Johnston wrote:
> On Tue, Aug 23, 2016 at 1:24 PM, Adrian Klaver
> <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>>wrote:
>
>
>     use ALTER TABLE ADD table_constraint :
>
>     https://www.postgresql.org/docs/9.5/static/sql-altertable.html
>     <https://www.postgresql.org/docs/9.5/static/sql-altertable.html>
>
>     to add the FK references to word_games.
>
>
> ​Hadn't considered "ALTER TABLE" but I'd be afraid of dump-restore
> hazards here.  Maybe pg_dump is smart enough to handle this correctly,
> though - maybe by adding constraint definitions after all tables and
> columns are present.

It does. Though the usual caveats about doing partial dumps apply, eg if
I had only specified -t fk_child below I would not get fk_parent
automatically:

postgres@test=# create table fk_child(id int, fk_id int);
CREATE TABLE
postgres@test=# create table fk_parent(id int, some_id int UNIQUE);
CREATE TABLE
postgres@test=# alter table fk_child ADD CONSTRAINT fk_constraint
FOREIGN KEY (fk_id) REFERENCES fk_parent(some_id);
ALTER TABLE

pg_dump -d test -U postgres  -t fk_parent -t fk_child -f test.sql


--
-- Name: fk_child; Type: TABLE; Schema: public; Owner: postgres
--

CREATE TABLE fk_child (
     id integer,
     fk_id integer
);


ALTER TABLE fk_child OWNER TO postgres;

--
-- Name: fk_parent; Type: TABLE; Schema: public; Owner: postgres
--

CREATE TABLE fk_parent (
     id integer,
     some_id integer
);


ALTER TABLE fk_parent OWNER TO postgres;

--
-- Data for Name: fk_child; Type: TABLE DATA; Schema: public; Owner:
postgres
--

COPY fk_child (id, fk_id) FROM stdin;
\.


--
-- Data for Name: fk_parent; Type: TABLE DATA; Schema: public; Owner:
postgres
--

COPY fk_parent (id, some_id) FROM stdin;
\.


--
-- Name: fk_parent_some_id_key; Type: CONSTRAINT; Schema: public; Owner:
postgres
--

ALTER TABLE ONLY fk_parent
     ADD CONSTRAINT fk_parent_some_id_key UNIQUE (some_id);


--
-- Name: fk_constraint; Type: FK CONSTRAINT; Schema: public; Owner: postgres
--

ALTER TABLE ONLY fk_child
     ADD CONSTRAINT fk_constraint FOREIGN KEY (fk_id) REFERENCES
fk_parent(some_id);


>
> David J.​
>


--
Adrian Klaver
adrian.klaver@aklaver.com