Re: Disallow unique index on system columns

On 2016-04-14 21:02:26 -0400, Tom Lane wrote:
> David Rowley <david.rowley@2ndquadrant.com> writes:
> > I proposed a fix over there, but it didn't go anywhere, probably
> > because Tom and Andres discussed just disallowing unique indexes on
> > system columns altogether. So, the attached patch does just that, and
> > also fixes up the replica identity bugs too, as it's still possible
> > that someone could create a unique index on a system column with an
> > old version, upgrade, then try to set the replica identity to that
> > index. We'd need to handle that correctly, so I fixed that too.
> 
> AFAIR, what we were discussing was disallowing any index on a system
> column (other than OID).  I do not see why only unique indexes are
> problematic for them; the semantic issues are independent of that.

+1