SELECT n.nspname AS namespace, p1.relname AS table,
a1.attname AS column
FROM pg_constraint c, pg_namespace n,
pg_class p1, pg_class p2,
pg_attribute a1, pg_attribute a2
WHERE c.contype = 'f'
AND c.confrelid >  0 
AND c.connamespace = n.oid
AND c.conrelid = p1.oid
AND c.confrelid = p2.oid
AND c.conrelid = a1.attrelid
AND a1.attnum = ANY (c.conkey)
AND c.confrelid = a2.attrelid
AND a2.attnum = ANY (c.confkey)
AND n.nspname = 'schema'
AND p2.relname = 'table_name'
order by p1.relname

A->B->C->Z->Y
       \
        Q->W