FULL JOIN on geometry = equality

[komzpa]

root=# create table aaa  as (select 'POINT(0 0)':: geometry as geom);
SELECT 1
root=# select * from aaa a full join aaa b on a.geom = b.geom;
ERROR:  FULL JOIN is only supported with merge-joinable or hash-joinable join conditions
root=# select * from aaa a full join aaa b on a.geom::bytea = b.geom::bytea;
                    geom                    |                    geom
--------------------------------------------+--------------------------------------------
 010100000000000000000000000000000000000000 | 010100000000000000000000000000000000000000
(1 row)

[komzpa]

In 17557:

Allow FULL OUTER JOIN on geometry.

Closes #4394
Closes ​https://github.com/postgis/postgis/pull/409

[robe]

okay I'm a bit disappointed the more common case of

 with mj as (select 'POINT(0 0)'::geometry geom) select '#4394', b.geom As b_geom, a.geom As a_geom from mj a full join mj b on ST_Intersects(a.geom, b.geom);

Does not work. Could it work? or is this the best we can do.

[robe]

I guess if we release this we should note it only works for equality?