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Re: Missing doc on expression format for ALTER TABLE

From: David Fetter <david(at)fetter(dot)org>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-docs(at)postgresql(dot)org
Subject: Re: Missing doc on expression format for ALTER TABLE
Date: 2005-03-28 16:22:44
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-docs
On Sun, Mar 27, 2005 at 09:50:47PM -0800, Josh Berkus wrote:
> Guys,
> > > Well, yes, actually.  Where in the documentation is a type
> > > conversion expression defined?   Do we use NEW and OLD?  Or the
> > > name of the column?  Or something else?
> >
> > I think the ALTER TABLE page is in dire need of a "See also"
> > section, at least.  And a reference to where <expression> is
> > defined would be nice to have.
> What I'm pointing out here is that the USING clause can't be just
> ANY expression, it needs to be a specific type of expression.   And
> the docs don't explain what kind of expression is usable here.
> Even a single example would go a long way ...

I sent a patch in awhile ago that added this:

"To change an integer column containing UNIX timestamps to timestamp
with time zone via a USING clause:

    ALTER COLUMN foo_timestamp TYPE timestamp with time zone
        timestamp with time zone 'epoch' + foo_timestamp * interval '1 second';

That is at least something, although I agree that more examples of the
exact kind of expression would be a very good thing.

David Fetter david(at)fetter(dot)org
phone: +1 510 893 6100   mobile: +1 415 235 3778

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