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Re: Inheritance

From: "Oliver Elphick" <olly(at)lfix(dot)co(dot)uk>
To: Jan Wieck <JanWieck(at)Yahoo(dot)com>
Cc: Ian Turner <vectro(at)pipeline(dot)com>, Oliver Elphick <olly(at)lfix(dot)co(dot)uk>, pgsql-general(at)postgresql(dot)org
Subject: Re: Inheritance
Date: 2000-07-31 05:40:08
Message-ID: 200007310540.e6V5eAA23294@linda.lfix.co.uk (view raw or flat)
Thread:
Lists: pgsql-general
Jan Wieck wrote:
  >> Yes, but what about referential integrity? Can I have a table column
  >> reference a column from Entities*? In my experimentation, this is not the
  >> case.
  >
  >    Referential integrity doesn't work with inheritance, and will
  >    not in 7.1.
  >
  >    It isn't possible to put a unique constraint on a  column  of
  >    Entities*  (AFAIK).  So that a SELECT pkey FROM Entities will
  >    never  return  any  duplicates?  The  RI  implementation   of
  >    PostgreSQL  doesn't  insist  on  such  a unique constraint to
  >    exist up to now, but it is required by the SQL specs and thus
  >    we'll do so someday.

The corollary of using RI on an inheritance tree is that there should be a
unique index on the primary keys of the whole tree.  If constraints could be
inherited, this would become available.

-- 
Oliver Elphick                                Oliver(dot)Elphick(at)lfix(dot)co(dot)uk
Isle of Wight                              http://www.lfix.co.uk/oliver
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                 ========================================
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