From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Jesper Pedersen <jesper.pedersen@redhat.com>,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15587: Partitions with ALTER TABLE ADD CONSTRAINT
In-reply-to: <201901151824.mxkelqcnfeq6@alvherre.pgsql>
References: <201901151824.mxkelqcnfeq6@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
	message dated "Tue, 15 Jan 2019 15:24:57 -0300"
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Content-ID: <2814.1547577776.1@sss.pgh.pa.us>
Date: Tue, 15 Jan 2019 13:42:56 -0500
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Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> On 2019-Jan-10, Jesper Pedersen wrote:
>> However, when you use ADD CONSTRAINT FOREIGN KEY you can't use ONLY, so
>> would it be a good idea to make ADD CONSTRAINT UNIQUE behave the same way,
>> i.e. error out ?

> I haven't investigated this angle.  It seems more complex than just a
> simple bugfix, right?

Wouldn't that be throwing away the entire point of the ONLY behavior,
ie to allow the component indexes to be built one at a time, without
holding locks across the whole partition tree?

I'm having a hard time getting from "ONLY confuses me" to "nobody
should be allowed to do this".  I think there is a documentation
and UX issue here, but I don't see that there's anything wrong
with the functionality.

			regards, tom lane