"David G. Johnston" <david.g.johnston@gmail.com> writes:
> There is no where clause so I'm doubtful there is much to be gained going
> down this path. The Index-Only scan seems like an optimal way to obtain
> this data and the existing query already does that.
The "index-only" scan is reported to do 86m heap fetches along the
way to returning 812m rows, so the data is apparently pretty dirty.
It's possible that a preliminary VACUUM to get page-all-visible hint
bits set would be a net win.
regards, tom lane