-- Cycle Query Cn

SELECT DISTINCT
e1.n1
FROM 
graph_100_5940 e1, 
graph_100_5940 e2, 
graph_100_5940 e3, 
graph_100_5940 e4, 
graph_100_5940 e5
WHERE
e1.n2 = e2.n1 AND
e2.n2 = e3.n1 AND 
e3.n2 = e4.n1 AND 
e4.n2 = e5.n1 AND 
e5.n2 = e1.n1


-- Cycle Query Cn
-- First Optimization
-- The query engine chooses a plan where it joins on the one hand 3 steps,
-- on the other hand 2 steps, and then combines these two intermediate
-- results into the final result by a sort merge join.
-- Here, we have pushed the duplicate elimination into the intermediate 
-- results.

SELECT DISTINCT
e123.n1
FROM 
(
    SELECT DISTINCT e1.n1, e3.n2 FROM
    graph_100_5940 e1, 
    graph_100_5940 e2, 
    graph_100_5940 e3 WHERE
    e1.n2 = e2.n1 AND
    e2.n2 = e3.n1 
) e123,
(
    SELECT  DISTINCT e4.n1, e5.n2 FROM
    graph_100_5940 e4, 
    graph_100_5940 e5 WHERE
    e4.n2 = e5.n1  
) e45
WHERE
e123.n2 = e45.n1 AND e123.n1 = e45.n2



-- Cycle Query Cn
-- Second Optimization
-- This query will be executed the engine as by the algorithm we developed.