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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Amit Langote <amitlangote09@gmail.com>,
        Michael Paquier <michael@paquier.xyz>,
        "David G. Johnston" <david.g.johnston@gmail.com>,
        Bruce Momjian <bruce@momjian.us>, phil.bayer@gmail.com,
        pgsql-docs@lists.postgresql.org,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Postgres 11: Table Partitioning and Primary Keys
In-reply-to: <20190709225333.GA18051@alvherre.pgsql>
References: <20190709225333.GA18051@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
	message dated "Tue, 09 Jul 2019 18:53:33 -0400"
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Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> That's a mild personal preference only though.  Anyway, based on your
> proposed wording, I wrote this:

>      <listitem>
>       <para>
>        Unique constraints on partitioned tables (as well as primary keys)
>        must constrain all the partition key columns.  This limitation exists
>        because <productname>PostgreSQL</productname> can only enforce
>        uniqueness in each partition individually.
>       </para>
>      </listitem>

> I'm not really sure about the "must constrain" verbiage.  Is that really
> comprehensible?

I think "must include" might be better.

> In CREATE TABLE, we already have this:
>      <para>
>       When establishing a unique constraint for a multi-level partition
>       hierarchy, all the columns in the partition key of the target
>       partitioned table, as well as those of all its descendant partitioned
>       tables, must be included in the constraint definition.
>      </para>

> which may not be the pinnacle of clarity, but took some time to craft
> and I think is correct.  Also it doesn't mention primary keys
> explicitly; maybe we should patch it by adding "(as well as a primary
> key)" right after "a unique constraint".  Thoughts?

I'd leave that alone.  I don't think the parenthetical comment about
primary keys in your new text is adding much either.

			regards, tom lane