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Re: [COMMITTERS] pgsql: Disallow changing/dropping default

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Dhanaraj(dot)M(at)Sun(dot)COM
Subject: Re: [COMMITTERS] pgsql: Disallow changing/dropping default
Date: 2006-06-27 18:34:41
Message-ID: 200606271834.k5RIYfS18334@momjian.us (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > Tom Lane wrote:
> >> Wasn't this patch rejected?
> 
> > Anyway, what is your opinion on this?
> 
> I thought we'd rejected it.  I'm not sure that we'd completely agreed
> what the best thing to do is, but what this patch actually does is to
> silently remove the dependency link.  That is, after
> 
> 	create table t1 (f1 serial);
> 	alter table t1 alter column f1 drop default;
> 
> t1_f1_seq is still there, but now completely unconnected to t1.
> That doesn't seem to me to satisfy the principle of least surprise.
> It's certainly not what the TODO item says (reject the DROP DEFAULT).
> I think we were considering the alternative of having the DROP DEFAULT
> remove the sequence, which probably could be implemented painlessly
> with a change in the way we set up the dependency links to start with.
> 
> In any case I don't like this patch: int/bool confusion, use of elog
> instead of ereport for a user-facing error message, failure to adhere to
> style guidelines for that message, etc.  (Although seeing that the error
> message is unreachable code, maybe that doesn't matter ;-))  Aside from
> the poor coding style, the whole idea of reaching into pg_depend to
> remove a single dependency strikes me as a brute-force solution to
> a problem that should have a more elegant answer.

Agreed, patch reverted.  Thanks for the analysis.

-- 
  Bruce Momjian   bruce(at)momjian(dot)us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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