On Wed, Mar 31, 2021 at 1:24 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I agree that we have some existing behavior that's related to this, but
> it's still messy, and I couldn't find any evidence that suggested that the
> runtime lookup costs anything. Typical subplans are going to deliver
> long runs of tuples from the same target relation, so as long as we
> maintain a one-element cache of the last lookup result, it's only about
> one comparison per tuple most of the time.
OK, that's pretty fair.
--
Robert Haas
EDB: http://www.enterprisedb.com