Re: Patch to add a primary key using an existing index

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>

To: Tom Lane <tgl@sss.pgh.pa.us>

Cc: Steve Singer <ssinger_pg@sympatico.ca>, Gurjeet Singh <singh.gurjeet@gmail.com>, PGSQL Hackers <pgsql-hackers@postgresql.org>, Peter Eisentraut <peter_e@gmx.net>, r t <pgsql@xzilla.net>, Itagaki Takahiro <itagaki.takahiro@gmail.com>

Date: 2011-01-25T00:56:06Z

Lists: pgsql-hackers

On Mon, Jan 24, 2011 at 7:01 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> One other issue that might be worthy of discussion is that as things
> stand, execution of the ADD CONSTRAINT USING INDEX syntax will cause
> the constraint to absorb the index as an INTERNAL dependency.  That
> means dropping the constraint would make the index go away silently ---
> it no longer has any separate life. If the intent is just to provide a
> way to get the effect of ALTER ADD PRIMARY KEY CONCURRENTLY, then this
> behavior is probably fine.  But someone who believes DROP CONSTRAINT
> exactly reverses the effects of ADD CONSTRAINT might be surprised.
> Comments?

Well, I think the behavior as described is what we want.  If the
syntax associated with that behavior is going to lead to confusion,
I'd view that as a deficiency of the syntax, rather than a deficiency
of the behavior.  (I make this comment with some reluctance
considering the amount of bikeshedding we've already done on this
topic, but... that's what I think.)

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company