Re: Alter column to type serial

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Thom Brown <thom(at)linux(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Alter column to type serial
Date: 2010-11-04 14:04:59
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers

Thom Brown <thom(at)linux(dot)com> writes:
> Would it be possible (or reasonable) to add support for changing the type of
> a column to serial or bigserial (yes, yes, I know they're not actual
> types)?

We've looked at that in the past and decided there were enough corner
cases that it wasn't clearly a good idea. In particular, what do you do
with the existing data in the column? What do you do if there's already
a DEFAULT expression for the column, throw it away? In particular, what
of the special case that the column is in fact already a serial, so the
default is pointing at an existing sequence?

It is possible to accomplish everything that such a command would do
manually, so the argument for having it boils down to wanting it to
be a bit easier. But unless the command can always do the right thing
automatically, I'm not sure "easy" is a good argument.

There's also the objection that such an operation would actually have
very little to do with ALTER COLUMN TYPE --- most of the things it would
do are not that. The fact that serial was bolted on as a fake type is a
wart that maybe we shouldn't extend in this particular fashion.

regards, tom lane

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message Dimitri Fontaine 2010-11-04 14:06:48 Re: ALTER OBJECT any_name SET SCHEMA name
Previous Message Robert Haas 2010-11-04 14:04:55 Re: contrib: auth_delay module