self-join-1.pig

edges     = LOAD 'graph.tsv' AS (v1:chararray, v2:chararray);
--
-- Augment the edges with the sizes of their outgoing adjacency lists.
--
grouped_edges = GROUP edges BY v1;
aug_edges     = FOREACH grouped_edges GENERATE FLATTEN(edges) AS (v1, v2), COUNT(edges) AS v1_out;
aug_dups      = FOREACH aug_edges GENERATE v1, v2, v1_out;
--
-- Compute the sizes of the intersections of outgoing adjacency lists
--
edges_joined  = JOIN aug_edges BY v2, aug_dups BY v2;
DUMP edges_joined;