Content-Type: text/plain; charset="utf-8"
Date: Wed, 27 Feb 2008 10:25:59 +0100
From: "Stefan Scheidegger" <Stefan.Scheidegger@gmx.net>
Message-ID: <20080227092559.261470@gmx.net>
MIME-Version: 1.0
Subject: REFERENCES and INHERITS restrictions?
To: pgsql-sql@postgresql.org
Content-Transfer-Encoding: 8bit

Hi all


I’m confronted with the following problem:

I have a base table with several child tables which also use the parent’s primary key as their own primary key:


CREATE TABLE tbl_parent
(
  p_id serial NOT NULL,
  p_time timestamp(6) with time zone NOT NULL DEFAULT '1970-01-01 01:00:00+01'::timestamp with time zone,
  CONSTRAINT tbl_parent_pkey PRIMARY KEY (p_id)
);

CREATE TABLE tbl_child1
(
  c1_something character varying(64) NOT NULL,
  CONSTRAINT tbl_child1_pkey PRIMARY KEY (p_id),
) INHERITS (tbl_parent);

CREATE TABLE tbl_child2
(
  c2_somethingelse integer NOT NULL,
  CONSTRAINT tbl_child2_pkey PRIMARY KEY (p_id),
) INHERITS (tbl_parent);


This works fine so far. Now I got another table that references to the primary key of the parent (I need an n to n relation between another table and an aggregation of all my child tables, which means an n to n relation between the other table and the parent table):


CREATE TABLE tbl_reference
(
  ref_id serial NOT NULL,
  ref_parent integer NOT NULL,
  ref_othertable integer NOT NULL,
  CONSTRAINT tbl_reference_pkey PRIMARY KEY (ref_id),
  CONSTRAINT tbl_reference_ref_parent_fkey FOREIGN KEY (ref_parent)
      REFERENCES tbl_parent (p_id) MATCH SIMPLE
      ON UPDATE CASCADE ON DELETE CASCADE,
  CONSTRAINT tbl_reference_ref_othertable_fkey FOREIGN KEY (ref_othertable)
      REFERENCES tbl_othertable (ot_id) MATCH SIMPLE
      ON UPDATE CASCADE ON DELETE SET NULL
)


When I try to insert into tbl_reference now, I get an sql error:

INSERT INTO tbl_child1(p_time,c1_something) VALUES ('2008-01-01', 'foo');
INSERT 0 1

SELECT * FROM tbl_parent;
 p_id |        p_time
------+------------------------
    1 | 2008-01-01 00:00:00+01
(1 row)

INSERT INTO tbl_reference(ref_parent,ref_othertable) VALUES ('1','1');
ERROR:  insert or update on table "tbl_reference" violates foreign key constrain
t "tbl_reference_ref_parent_fkey"
DETAIL:  Key (ref_parent)=(1) is not present in table "tbl_parent".


Why is this not possible? It seems that this is about inheritance. When I reference directly to tbl_child1, everything works just fine.

Any idea?


Greets Stefan

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