I have a table which contains the edges from node x to node y in a graph.
n1 | n2
-------
a | a
a | b
a | c
b | b
b | d
b | c
d | e
I would like to create a (materialized) view which denotes the shortest number of nodes/hops a path contains to reach from x to node y:
n1 | n2 | c
-----------
a | a | 0
a | b | 1
a | c | 1
a | d | 2
a | e | 3
b | b | 0
b | d | 1
b | c | 1
b | e | 2
d | e | 1
How should I model my tables and views to facilitate this? I guess I need some kind of recursion, but I believe that is pretty difficult to accomplish in SQL. I would like to avoid that, for example, the clients need to fire 10 queries if the path happens to contain 10 nodes/hops.