I am using pgr_ksp algorithm to find out the shortest path between a startnode and endnode by creating a network topology between all the nodes. Pgr_ksp algorithm very well gives me all the shortest paths taking the cost in consideration. But now, I also want to add a constraint that the path its giving between startnode and endnode must include a particular node or link. Below code works perfect. But how and where can I add a constraint such that the path will include a node for example 'nodeA'?

SELECT d.*, f.linkname ,SUM(cost) OVER (PARTITION BY path_id) AS aggregation
FROM pgr_ksp('Select id, source, target, airmiles as cost from express1_path',
source,
target,
 2) AS d
INNER JOIN f ON d.edge= f.id
ORDER BY aggregation, path_id, path_seq;