On 2015-11-30 12:58:43 -0500, Bruce Momjian wrote:
> I would not bother mentioning this detail in the pg_upgrade manual page:
>
> + Since the format of visibility map has been changed in version 9.6,
> + <application>pg_upgrade</> creates and rewrite new <literal>'_vm'</literal>
> + file even if upgrading from 9.5 or before to 9.6 or later with link mode (-k).
Might be worthwhile to keep as that influences the runtime for link mode
when migrating <9.6 -> 9.6.