Re: FULL JOIN is only supported with merge-joinable join conditions

> It's an implementation restriction.  If the clauses aren't mergejoinable
> there's no very practical way to keep track of which inner-side rows
> have had a match.


If we could consider it is equivalent transformation as follow?

select * from t_1 full outer join t_3 on t_1.a=1;
and
select * from t_1 full outer join t_3 on true where t_1.a=1;

If we could transform RestrictInfo into the where-clause, maybe it right.

TEST=# select * from t_1 full outer join t_3 on true where t_1.a=1;
 A | A
---+---
 1 | 1
 1 | 3
(2 rows)