触发器可能违反postgresql中的外键

我试图创建一个简单的示例,显示外键约束被强制执行。通过这个例子,我证明了我不允许输入违反fk的数据,并且证明了如果在插入期间fk不在适当的位置,并且我启用了fk,fk约束将抛出一个错误,告诉我数据违反了fk。所以我没有看到表中的数据是如何违反fk的。我是9.0版的,但8.3版应该没什么不同。如果你能展示一个能证明你的问题的有效例子,也许会有帮助。

--CREATE TABLES--
CREATE TABLE parent
(
  parent_id integer NOT NULL,
  first_name character varying(50) NOT NULL,
  CONSTRAINT pk_parent PRIMARY KEY (parent_id)
)
WITH (
  OIDS=FALSE
);
ALTER TABLE parent OWNER TO postgres;

CREATE TABLE child
(
  child_id integer NOT NULL,
  parent_id integer NOT NULL,
  first_name character varying(50) NOT NULL,
  CONSTRAINT pk_child PRIMARY KEY (child_id),
  CONSTRAINT fk1_child FOREIGN KEY (parent_id)
      REFERENCES parent (parent_id) MATCH SIMPLE
      ON UPDATE CASCADE ON DELETE CASCADE
)
WITH (
  OIDS=FALSE
);
ALTER TABLE child OWNER TO postgres;
--CREATE TABLES--

--INSERT TEST DATA--
INSERT INTO parent(parent_id,first_name)
SELECT 1,'Daddy'
UNION 
SELECT 2,'Mommy';

INSERT INTO child(child_id,parent_id,first_name)
SELECT 1,1,'Billy'
UNION 
SELECT 2,1,'Jenny'
UNION 
SELECT 3,1,'Kimmy'
UNION 
SELECT 4,2,'Billy'
UNION 
SELECT 5,2,'Jenny'
UNION 
SELECT 6,2,'Kimmy';
--INSERT TEST DATA--

--SHOW THE DATA WE HAVE--
select parent.first_name,
       child.first_name
from parent
inner join child
        on child.parent_id = parent.parent_id
order by parent.first_name, child.first_name asc;
--SHOW THE DATA WE HAVE--

--DELETE PARENT WHO HAS CHILDREN--
BEGIN TRANSACTION;
delete from parent
where parent_id = 1;

--Check to see if any children that were linked to Daddy are still there?
--None there so the cascade delete worked.
select parent.first_name,
       child.first_name
from parent
right outer join child
        on child.parent_id = parent.parent_id
order by parent.first_name, child.first_name asc;
ROLLBACK TRANSACTION;


--TRY ALLOW NO REFERENTIAL DATA IN--
BEGIN TRANSACTION;

--Get rid of fk constraint so we can insert red headed step child
ALTER TABLE child DROP CONSTRAINT fk1_child;

INSERT INTO child(child_id,parent_id,first_name)
SELECT 7,99999,'Red Headed Step Child';

select parent.first_name,
       child.first_name
from parent
right outer join child
        on child.parent_id = parent.parent_id
order by parent.first_name, child.first_name asc;

--Will throw FK check violation because parent 99999 doesn't exist in parent table
ALTER TABLE child
  ADD CONSTRAINT fk1_child FOREIGN KEY (parent_id)
      REFERENCES parent (parent_id) MATCH SIMPLE
      ON UPDATE CASCADE ON DELETE CASCADE;

ROLLBACK TRANSACTION;
--TRY ALLOW NO REFERENTIAL DATA IN--

--DROP TABLE parent;
--DROP TABLE child;

到目前为止,我读到的所有内容似乎都表明,只有在插入数据时才检查约束。(或在创建约束时)例如 the manual on set constraints

这是有意义的-如果数据库工作正常-应该足够好。

不管怎样,结案:-/

肯定有一个约束冲突,是由一个错误的触发器引起的。下面是要复制的脚本:

-- Create master table
CREATE TABLE product
(
  id INT NOT NULL PRIMARY KEY
);

-- Create second table, referencing the first
CREATE TABLE example
(
  id int PRIMARY KEY REFERENCES product (id) ON DELETE CASCADE
);

-- Create a (broken) trigger function
--CREATE LANGUAGE plpgsql;
CREATE OR REPLACE FUNCTION delete_product()
  RETURNS trigger AS
$BODY$
    BEGIN
      DELETE FROM product WHERE product.id = OLD.id;
      -- This is an error!
      RETURN null;
    END;
$BODY$
  LANGUAGE plpgsql;

-- Add it to the second table
CREATE TRIGGER example_delete
  BEFORE DELETE
  ON example
  FOR EACH ROW
  EXECUTE PROCEDURE delete_product();

-- Now lets add a row
INSERT INTO product (id) VALUES (1);
INSERT INTO example (id) VALUES (1);

-- And now lets delete the row
DELETE FROM example WHERE id = 1;

/*
Now if everything is working, this should return two columns:
(pid,eid)=(1,1). However, it returns only the example id, so
(pid,eid)=(0,1). This means the foreign key constraint on the
example table is violated.
*/
SELECT product.id AS pid, example.id AS eid FROM product FULL JOIN example ON product.id = example.id;