Negative cache entries for memoize

I wrote an optimizer talk that explains memoize, slides 24-25:

    https://momjian.us/main/writings/pgsql/beyond.pdf#page=25

During two presentations, I was asked if negative cache entries were
created for cases where inner-side lookups returned no rows.

It seems we don't do that.  Has this been considered or is it planned?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Embrace your flaws.  They make you human, rather than perfect,
  which you will never be.