"hx.li" <fly2nn(at)126(dot)com> writes:
> ERROR: FULL JOIN is only supported with merge-joinable join conditions
> My question is: why on clause restrict "t_1.a=1"?
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.
> I test it in Oracle, it support to such as "t_1.a=1":
I'd be interested to know how whatever they're doing scales to very
large joins.
regards, tom lane