Re: [ADMIN] delete cascade question

[Glenn MacGregor]

Sorry for being too vague. Here is my exact situation.
I have the following table currently:
                                           Table "xpressvim"
       Column        |          Type          | 
Modifiers
---------------------+------------------------+---------------------------------------------------------
 vimid               | integer                | not null default 
nextval('"xpressvim_vimid_seq"'::text)
 vimname             | character varying(128) | not null
 vimclass            | character varying(50)  | not null
 isadmin             | boolean                | not null default 'f'
 adminname           | character varying(136) |
 vimtype             | character varying(64)  |
 deviceconfig        | character varying(64)  |
 deviceip            | inet                   |
 parentname          | character varying(128) |
 discovereditemindex | bigint                 |
 islicensed          | boolean                |
 addevgroupname      | character varying(64)  |
Primary key: xpressvim_pkey
Unique keys: xpressvim_vimname_key
Triggers: RI_ConstraintTrigger_16786,
          RI_ConstraintTrigger_16788,
          RI_ConstraintTrigger_16792,
          RI_ConstraintTrigger_16794,
          RI_ConstraintTrigger_16802,
          RI_ConstraintTrigger_16804,
          RI_ConstraintTrigger_16846

The constraint that I am concerned with here is the following:
CREATE CONSTRAINT TRIGGER "<unnamed>" AFTER DELETE ON "xpressvim"  FROM 
"xpressvim" NOT DEFERRABLE INITIALLY IMMEDIATE FOR EACH ROW EXECUTE 
PROCEDURE "RI_FKey_cascade_del" ('<unnamed>', 'xpressvim', 'xpressvim', 
'UNSPECIFIED', 'parentname', 'vimname');

Example data:
vimid | vimname | vimclass | isadmin | adminname | vimtype | 
deviceconfig | deviceip | parentname | discovereditemindex | islicensed 
| addevgroupname

1 | [EMAIL PROTECTED] | cell | f | [EMAIL PROTECTED] | cell | test.xml | 
192.168.0.23 | | 1 | t | group1

2 | [EMAIL PROTECTED] | cell | f | [EMAIL PROTECTED] | cell | test_if.xml | 
192.168.0.23 | [EMAIL PROTECTED] | 2 | t | group1

So the above constraint says if I delete row 1 (vimid = 1) then row 2 
(vimid = 2) should be deleted as well because I an deleting the parent 
of 2. This works fine.

Now I need to change the parentname field (in the case of vimid = 2) 
from [EMAIL PROTECTED] to test and keep the vimname field as is. When I do 
this the constraint no longer works (which makes perfect sense).

1 | [EMAIL PROTECTED] | cell | f | [EMAIL PROTECTED] | cell | test.xml | 
192.168.0.23 | | 1 | t | group1

2 | [EMAIL PROTECTED] | cell | f | [EMAIL PROTECTED] | cell | test_if.xml | 
192.168.0.23 | test | 2 | t | group1

delete row 1 and row 2 stays around.
Is there a way to create a constraint that will delete row 2 if I delete 
row 1 using a substring of the vimname to match with the parentname?

        Thanks
                Glenn


Greg Sabino Mullane wrote:
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Hash: SHA1
 
 

I am using a cascade delete on the following table:
...
So the delete cascade states if I am deleting a row whose vname
matches the parentname delete those rows and it works fine.
...
This works, so I tried to put that in the cascade but it failed.
 
Not sure what you mean by "put that in the cascade." You will have
to show us your actual tables and contraints. In general, "on delete cascade"
refers to what happens to foreign key rows when the referenced key is
deleted. Similarly, you can set a constraint as "on update cascade"
in which case the changes in the parent table are also made in the child
tables. Here is a quick example that may help:
 
CREATE TABLE "myparent" (
  "a" INTEGER,
  "b" TEXT unique
);
 
CREATE TABLE "mychild" (
  "c" INTEGER,
  "d" TEXT NOT NULL
);
 
ALTER TABLE "mychild" ADD CONSTRAINT "mychild_d_fk"
  FOREIGN KEY (d) REFERENCES myparent(b)
  ON DELETE CASCADE ON UPDATE CASCADE;
 
INSERT INTO myparent(a,b) VALUES (1,'Garibaldi');
INSERT INTO myparent(a,b) VALUES (2,'Zathras');
INSERT INTO myparent(a,b) VALUES (3,'G''Kar');
 
- -- This fails, because the foreign key constraint catches the typo:
INSERT INTO mychild(c,d) VALUES (1,'Garabaldi');
 
INSERT INTO mychild(c,d) VALUES (9,'Garibaldi');
INSERT INTO mychild(c,d) VALUES (10,'Zathras');
INSERT INTO mychild(c,d) VALUES (11,'Zathras');
 
SELECT * FROM mychild;
 
greg=# SELECT * FROM mychild;
 c  |     d
- ----+-----------
  9 | Garibaldi
 10 | Zathras
 11 | Zathras
 
 
UPDATE myparent SET b = 'Chief' WHERE b='Garibaldi';
 
- -- ON UPDATE CASCADE has changed the name in both tables:
 
SELECT * FROM mychild;
 
 c  |    d
- ----+---------
 10 | Zathras
 11 | Zathras
  9 | Chief
 
DELETE FROM myparent WHERE b = 'Zathras';
 
- -- ON DELETE CASCADE has removed all the Zathras's
 
SELECT * FROM mychild;
 
 c |   d
- ---+-------
 9 | Chief
 
 
- --
Greg Sabino Mullane [EMAIL PROTECTED]
PGP Key: 0x14964AC8 200404262305
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