"hx.li" <fly2nn(at)126(dot)com> writes:
> 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;
Those are not equivalent.
regards, tom lane