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Re: Add column if not exists (CINE)

From: Dimitri Fontaine <dfontaine(at)hi-media(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, Kjell Rune Skaaraas <kjella79(at)yahoo(dot)no>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Add column if not exists (CINE)
Date: 2010-04-28 17:40:55
Message-ID: m24oiv5vbs.fsf@hi-media.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Well, how would you define CREATE OR REPLACE TABLE?  I think that
> doesn't make much sense, which is why I think CREATE IF NOT EXISTS is
> a reasonable approach.

<hand waving time>

The behavior I'd like to have would be to allow me to give a SELECT
query to run for replacing what is there if there's something. If the
query can not be run on the existing data set, error out of course.

So you know the state for sure after the command, but it depends on your
query being correct. And you can (de)normalize existing data using joins.

The REPLACE keyword would here mean that there's a CTAS going under the
hood, then we add the constraints and indexes and triggers etc. That
would mean being able to express those entities changes too, but it
seems important.

Well, that may be not precise enough as a spec, but at least that's food
for though I hope.

Regards,
-- 
dim

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