Re: What does "merge-joinable join conditions" mean ????

"Dean Gibson (DB Administrator)" <postgresql4(at)ultimeth(dot)com> writes:
> I have a FULL JOIN between two simple tables, and am getting the message
> " Query failed: ERROR: FULL JOIN is only supported with merge-joinable
> join conditions"

> I'd be glad to fix this in my query if I knew what the #(at)!! it meant.

The join condition(s) of a FULL JOIN have to be mergejoinable, which
basically means an equality relation between sortable (btree-indexable)
data types. You can see exactly which operators are mergejoinable with
a query like

select oid::regoperator from pg_operator where oprlsortop != 0;

regards, tom lane