Florian Weimer <Florian(dot)Weimer(at)RUS(dot)Uni-Stuttgart(dot)DE> writes:
> Is there some efficient PostgreSQL expression which is true if and
> only if two subnets (given as values of type cidr) have non-empty
> intersection (even if the intersection is not a CIDR network)?
Maybe I'm missing something, but ISTM it's only possible for two
CIDR subnets to overlap if one contains the other. So you could
check with
A <<= B OR B <<= A
regards, tom lane