Re: Use merge-based matching for MCVs in eqjoinsel

I wrote:
> Actually, after sleeping on it it seems like the obvious thing is
> to test "sslot1.nvalues * sslot2.nvalues", since the work we are
> thinking about saving scales as that product.  But I'm not sure
> what threshold value to use if we do that.  Maybe around 10000?

Or maybe better, since we are considering an O(m*n) algorithm
versus an O(m+n) one, we could check whether

sslot1.nvalues * sslot2.nvalues - (sslot1.nvalues + sslot2.nvalues)

exceeds some threshold.  But that doesn't offer any insight into
just what the threshold should be, either.

            regards, tom lane