Re: Materialized views and unique indexes

On Fri, Mar 8, 2013 at 12:32 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Craig Ringer <craig(at)2ndquadrant(dot)com> writes:
> > On 03/08/2013 10:55 AM, Michael Paquier wrote:
> >> Also, as it is not mandatory for a unique index to be a constraint, I
> >> think that we should block the creation of unique indexes too to avoid
> >> any problems. Any suggestions?
>
> > How much does the planner benefit from the implied constraint of a
> > unique index? I almost wonder if it should be allowed at the cost of
> > making the refresh of a matview that fails to comply an error.
>
> A unique constraint can allow join elimination, so I'm thinking that
> disallowing them is a bad idea (not to mention that it'd be a
> considerable wart in the code to block them for matviews only).
>
Fair argument.

The error message at refresh step should be more explicit though. I still
have the feeling that users might be lost if a constraint introduced on
matviews is failing during refresh with the current error message.
--
Michael