Re: [COMMITTERS] pgsql: Disallow changing/dropping default - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: [COMMITTERS] pgsql: Disallow changing/dropping default
Date
Msg-id 200606271834.k5RIYfS18334@momjian.us
Whole thread Raw
In response to Re: [COMMITTERS] pgsql: Disallow changing/dropping default expression  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
Tom Lane wrote:
> Bruce Momjian <bruce@momjian.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@momjian.us EnterpriseDB    http://www.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +


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