Re: What order of steps of the postgres when you change information in the table?

On Fri, 30 Oct 2009 23:29:49 -0600
Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> wrote:

> 2009/10/30 Denis Feklushkin <denis(dot)feklushkin(at)gmail(dot)com>:
> >
> > Problem:
> > It is necessary to synchronize the "users" table with an
> > external storage of passwords (krb5)
> >
> > I made a trigger:
> >
> > CREATE TRIGGER "10_krb5"
> >  AFTER INSERT OR UPDATE OR DELETE
> >  ON users
> >  FOR EACH ROW
> >  EXECUTE PROCEDURE user2krb5_python();
> >
> > Everything works, except that when you delete a row from table
> > "users" foreign keys checking occurs after this trigger. And in case
> > of any problems with the referencing record is an exception,
> > rollback is occured (this is ok), but the trigger
> > user2krb5_python() was executed and the user from the external
> > storage removed.
> >
> > Checking of foreign keys occurs after the "AFTER-trigger" is ok?
> > Check of the primary key, unique, and other constraints occurs in
> > the very beginning, I checked.
>
> The common solution here is to put a record into a table and issue a
> notify to a listening process to take that table and process it.
> Since a notify only fires if the transaction completes without error,
> and the entry in the table won't exist unless the transaction
> completes, the external process won't be kicked off unless the things
> are complete.

If an error occurs in an external process? Transaction will not
be interrupted because it will be finished.

It seems to me, checking of the foreign key after all
triggers is meaningless