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List:       postgresql-general
Subject:    Re: [GENERAL] pg_dumpall and check constraints
From:       JanWieck () t-online ! de (Jan Wieck)
Date:       2000-06-30 15:56:19
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Guillaume Perréal wrote:
> > 
> > OR
> > 
> > 2. create a view:
> > create view "station_fields" as select * from information where fieldname = \
> > 'station.type'; 
> > then use:
> > 
> > FOREIGN KEY ( "type") references "station_fields" ( code),
> 
> I tried : it doesn't work. It seems that view rows don't have OID, which are used \
> in foreign key. (I deduce that from the error messages I've got  when I tried). 

    For  gods  sake  they  don't have.  And I'm uncertain that it
    should ever work.

    The reason is that an  FK  constraint  not  only  has  to  be
    checked  at  INSERT/UPDATE  time of the referencing table. It
    must  further  ensure  that  later   modifications   to   the
    referenced  table  don't  violate existing references. Now in
    the case of a view that is a join over 3 tables, we  setup  a
    multicolumn  FK constraint over columns coming from different
    base tables (or computed ones). How should a RESTRICT  or  ON
    DELETE CASCADE work in that scenario?


Jan

--

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