Re: Idea on how to simplify comparing two sets

"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> On Tue, Feb 7, 2017 at 8:58 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Joel Jacobson <joel(at)trustly(dot)com> writes:
>>> Currently there is no simple way to check if two sets are equal.

>> Uh ... maybe check whether SELECT set1 EXCEPT SELECT set2
>> and SELECT set2 EXCEPT SELECT set1 are both empty?

> ​SELECT set1 FULL EXCEPT SELECT set2 ?
> Matches with the concept and syntax of "FULL JOIN"​.

Actually ... now that you mention full join, I believe this works:

select * from (select ...) s1 full join (select ...) s2
on ((s1.*)=(s2.*)) where s1.* is distinct from s2.*;

> That said I'm not sure how much we want to go down this road on our own.
> It'd be nice to have when its needed but its not something that gets much
> visibility on these lists to suggest a large pent-up demand.

Yeah, if this isn't in the standard and not in other databases either,
that would seem to suggest that it's not a big requirement.

regards, tom lane