Re: [HACKERS] Index only scan for cube and seg

Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, Oct 26, 2017 at 12:22 PM, Andrey Borodin <x4mmm@yandex-team.ru> wrote:
>> For cube there is new default opclass.

> I seem to recall that changing the default opclass causes unsolvable
> problems with upgrades.  You might want to check the archives for
> previous discussions of this issue; unfortunately, I don't recall the
> details off-hand.

Quite aside from that, replacing the opclass with a new one creates
user-visible headaches that I don't think are justified, i.e. having to
reconstruct indexes in order to get the benefit.

Maybe I'm missing something, but ISTM you could just drop the compress
function and call it good.  This would mean that an IOS scan would
sometimes hand back a toast-compressed value, but what's the problem
with that?

(The only reason for making a decompress function that just detoasts
is that your other support functions then do not have to consider
the possibility that they're handed a toast-compressed value.  I have
not checked whether that really matters for cube.)