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Re: Re: Changing the default value of an inherited column

From: "Oliver Elphick" <olly(at)lfix(dot)co(dot)uk>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Re: Changing the default value of an inherited column
Date: 2001-03-29 13:29:38
Message-ID: 200103291329.f2TDTd324709@linda.lfix.co.uk (view raw or flat)
Thread:
Lists: pgsql-hackers
Peter Eisentraut wrote:
  >Tom Lane writes:
  >
  >> It seems that in pre-7.0 Postgres, this works:
  >>
  >> create table one(id int default 1, descr text);
  >> create table two(id int default 2, tag text) inherits (one);
  >>
  >> with the net effect that table "two" has just one "id" column with
  >> default value 2.
  >
  >Although the liberty to do anything you want seems appealing at first, I
  >would think that allowing this is not correct from an OO point of view.

I don't agree; this is equivalent to redefinition of a feature (=method) in
a descendant class, which is perfectly acceptable so long as the feature's
signature (equivalent to column type) remains unchanged.

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