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.
regards, tom lane