Fix issue ksp 1891

NEWS

@@ -1,6 +1,11 @@
 pgRouting 3.4.0 Release Notes
 -------------------------------------------------------------------------------
 
+**Issue fixes**
+
+* [#1891](https://github.com/pgRouting/pgrouting/issues/1891):
+  pgr_ksp doesn't give all correct shortest path
+
 **New proposed functions**
 
 * With points

doc/src/release_notes.rst

@@ -38,6 +38,11 @@ To see the full list of changes check the list of `Git commits
 pgRouting 3.4.0 Release Notes
 -------------------------------------------------------------------------------
 
+.. rubric:: Issue fixes
+
+* `#1891 <https://github.com/pgRouting/pgrouting/issues/1891>`__:
+  pgr_ksp doesn't give all correct shortest path
+
 .. rubric:: New proposed functions
 
 * With points

include/yen/pgr_ksp.hpp

@@ -169,7 +169,7 @@ class Pgr_ksp :  public Pgr_messages {
              auto rootPath = curr_result_path.getSubpath(i);
 
              for (const auto &path : m_ResultSet) {
-                 if (path.isEqual(rootPath)) {
+                 if (path.isEqual(rootPath) && spurNodeId == path[i].node) {
                      if (path.size() > i + 1) {
                          graph.disconnect_edge(path[i].node,     // from
                                  path[i + 1].node);  // to

pgtap/ksp/ksp/edge_cases/issue_1891.pg

@@ -0,0 +1,63 @@
+BEGIN;
+
+SELECT CASE WHEN min_version('3.4.0') THEN plan(2) ELSE plan(1) END;
+
+CREATE TABLE fiber(id SERIAL, source INT, target INT, cost FLOAT);
+
+INSERT INTO FIBER (source, target, cost) VALUES
+(1,2,10),(2,4,10),(1,3,10),(3,4,10),(2,3,10),(1,4,10);
+
+
+CREATE OR REPLACE FUNCTION issue_1891() RETURNS SETOF TEXT AS
+$BODY$
+DECLARE
+  have INTEGER;
+BEGIN
+  IF NOT min_version('3.4.0') THEN
+    RETURN QUERY SELECT skip(1, 'Issue fixed on 3.4.0');
+    RETURN;
+  END IF;
+
+SELECT count(DISTINCT path_id) FROM
+pgr_ksp('SELECT * FROM fiber', 1, 4, 10, directed => false, heap_paths => true) INTO have;
+
+RETURN QUERY
+SELECT is(have, 5);
+
+prepare q2 AS
+SELECT * FROM
+pgr_ksp('SELECT * FROM fiber', 1, 4, 10, directed => false, heap_paths => true);
+
+PREPARE r2 AS
+SELECT *
+FROM (VALUES
+  (1, 1, 1, 1, 6, 10, 0),
+  (2, 1, 2, 4, -1, 0, 10),
+  (3, 2, 1, 1, 1, 10, 0),
+  (4, 2, 2, 2, 2, 10, 10),
+  (5, 2, 3, 4, -1, 0, 20),
+  (6, 3, 1, 1, 3, 10, 0),
+  (7, 3, 2, 3, 4, 10, 10),
+  (8, 3, 3, 4, -1, 0, 20),
+  (9, 4, 1, 1, 1, 10, 0),
+  (10,4, 2, 2, 5, 10, 10),
+  (11, 4, 3, 3, 4, 10, 20),
+  (12, 4, 4, 4, -1, 0, 30),
+  (13, 5, 1, 1, 3, 10, 0),
+  (14, 5, 2, 3, 5, 10, 10),
+  (15, 5, 3, 2, 2, 10, 20),
+  (16, 5, 4, 4, -1, 0, 30))
+AS t(seq, path_id, path_seq, node, edge, cost, agg_cost);
+
+RETURN QUERY
+SELECT bag_eq('q2','r2','q2 should have r2 result');
+
+END
+$BODY$
+LANGUAGE plpgsql VOLATILE;
+
+
+SELECT issue_1891();
+
+SELECT finish();
+ROLLBACK;