Re: Postgres 11: Table Partitioning and Primary Keys

Alvaro Herrera <alvherre(at)2ndquadrant(dot)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