Recursive grouping and bucket assignment

gistfile1.sql

with
-- Shamelessly stolen from                                                                                                                                                                      
-- http://www.postgresql.org/docs/9.3/static/queries-with.html                                                                                                                                  
    recursive groups (key1, key2, path, cycle)
AS  (
        select  key1,
                key2,
                ARRAY[ROW(key1, key2)],
                false
        from    graph
        union all
        select  a.key1,
                b.key2,
                path || ROW(a.key1, b.key2),
                ROW(a.key1, b.key2) = ANY(PATH)
        from    graph a,
                groups b
        where   (a.key1 = b.key2 OR a.key2 = b.key1)
            and not cycle
    )

select      groups.key1,                                                                                                                                                                        
            dense_rank() OVER (order by min(groups.key2)) as bucket                                                                                                                             
from        groups
group by    groups.key1                                                                                                                                                                         
order by    groups.key1; 

You have made the world a better place.