Re: Block nested loop join

Gregory Stark <stark@enterprisedb.com> writes:
> So the use case of a real block nested loop would be doing a cartesian join of
> two large tables where neither fits in RAM. That does seem like it might be
> kind of narrow given how large the output would be.

Yeah.  If you have a hashable join condition then our existing batched
hash join code should be roughly equivalent to this method.  So the use
case is joining a couple of large tables with an un-hashable,
un-indexable join condition (or none at all, ie cross product) and that
just isn't something we hear people wanting to do a lot.  I can't really
see why we'd bother maintaining extra code for block nested loop.
        regards, tom lane