Re: Avoiding hash join batch explosions with extreme skew and weird stats

Admittedly I don't have a patch, just a bunch of handwaving.  One
reason I haven't attempted to write it is because although I know how
to do the non-parallel version using a BufFile full of match bits in
sync with the tuples for outer joins, I haven't figured out how to do
it for parallel-aware hash join, because then each loop over the outer
batch could see different tuples in each participant.  You could use
the match bit in HashJoinTuple header, but then you'd have to write
all the tuples out again, which is more IO than I want to do.  I'll
probably start another thread about that.