Обсуждение: How to discover foreign keys (without pulling hair out)

Given a particular table, I want to get a list of all the foreign keys and
what they refer to, something like:
local table | local field | foreign table | foreign field
-------------+-------------+---------------+---------------companies   | prime       | contacts      |
contact_idcompanies  | referer     | contacts      | contact_idcontacts    | company_id  | companies     | company_id
 
etc..

Here's as far as I've gotten:

To find the foreign keys in the "companies" table, do:

SELECT  tgargs
FROM    pg_trigger
WHERE   tgrelid = (select oid from pg_class where relname='companies')       AND       tgfoid = (select oid from
pg_procwhere proname='RI_FKey_check_ins')
 
;
                                     tgargs
-----------------------------------------------------------------------------
co.pri-c\000companies\000contacts\000UNSPECIFIED\000prime\000contact_id\000
co.ref-c\000companies\000contacts\000UNSPECIFIED\000referer\000contact_id\000
(2 rows)

These are the 6 args to the RI_FKey_check_ins function that is called in
relation to foreign key checking.

1 = trigger name
2 = local table
3 = foreign table
4 = ? (what is this one?)
5 = local field
6 = foreign field

With painstaking use of position(), octet_length(), and substring(), one can
extract the appropriate fields. Here's just one:

select substring( (   select substring(     tgargs,     ( position('\\000'::bytea in tgargs)       +
octet_length('\\000companies\\000'::bytea)    )   ) from test limit 1 ) from 1 for (   select position('\\000'::bytea
in    (       select substring(         tgargs,         ( position('\\000'::bytea in tgargs)           +
octet_length('\\000companies\\000'::bytea)        )       ) from test limit 1     )   ) ) - 1
 
) as foreign_table;
foreign_table
---------------contacts
(1 row)

Obviously, if there's an easier way, I'm all ears. BTW, I would like to
avoid custom functions if at all possible.

Regards,
Ian Morgan
-- 
-------------------------------------------------------------------Ian E. Morgan        Vice President & C.O.O.
Webcon,Inc.imorgan@webcon.net         PGP: #2DA40D07          www.webcon.net   *  Customized Linux network solutions
foryour business  *
 
-------------------------------------------------------------------

Hi,

I use pgAdminII on Windows. It connects to a PostgreSQL
on a Linux PC.
When you click on an existing table's icon, it shows you
a script that could have created it (it detects the
structure of the table by itself), including the foreign
keys.
That's an easy way. But maybe not very elegant...

-- Table: slip
CREATE TABLE "slip" ( "id_slip" int4 DEFAULT nextval
('"slip_id_slip_seq"'::text) NOT NULL, "proprio" int4, CONSTRAINT "slip_pkey" PRIMARY KEY ("id_slip"), CONSTRAINT
"slip_de"FOREIGN KEY ("proprio") 
REFERENCES "maitre" ("maitre_id") ON DELETE NO ACTION ON
UPDATE NO ACTION NOT DEFERRABLE INITIALLY IMMEDIATE
);
COMMENT ON TABLE "slip" IS 'les slobards en folie !';
-------------------
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On Thu, 25 Apr 2002, bob lapique wrote:

> I use pgAdminII on Windows. It connects to a PostgreSQL on a Linux PC.
> When you click on an existing table's icon, it shows you a script that
> could have created it (it detects the structure of the table by itself),
> including the foreign keys. That's an easy way. But maybe not very
> elegant...

I have in fact tried that very thing. pgAdminII has a Log View that is
supposed to show all the back-end SQL that it executes in order to show you
what it does. However, all it really does is retrieve the pg_triggers.tgargs
field, which is 6 fields separated by \0's, then it must parse it internally.

I'm looking for a way to parse 'one\000two\000three\000'::bytea into
foo1 | foo2 | foo3
------+------+-------one  | two  | three

using only (Postgre)SQL, no external C functions or the like. Ideas? I'm
looking into PL/pgSQL as a solution, but haven't gotten very far yet.


Regards,
Ian Morgan
-- 
-------------------------------------------------------------------Ian E. Morgan        Vice President & C.O.O.
Webcon,Inc.imorgan@webcon.net         PGP: #2DA40D07          www.webcon.net   *  Customized Linux network solutions
foryour business  *
 
-------------------------------------------------------------------