Add exception to recognize cyclic relational graph

sap-contributions · Dec 11, 2023 · b758f4a · b758f4a
1 parent 849a65a
commit b758f4a
Showing 1 changed file with 11 additions and 6 deletions.
diff --git a/core/src/main/java/org/apache/calcite/plan/volcano/RelSubset.java b/core/src/main/java/org/apache/calcite/plan/volcano/RelSubset.java
@@ -388,7 +388,7 @@ void add(RelNode rel) {
    */
   RelNode buildCheapestPlan(VolcanoPlanner planner) {
     CheapestPlanReplacer replacer = new CheapestPlanReplacer(planner);
-    final RelNode cheapest = replacer.visit(this, -1, null);
+    final RelNode cheapest = replacer.visit(this, -1);
 
     if (planner.getListener() != null) {
       RelOptListener.RelChosenEvent event =
@@ -621,17 +621,22 @@ private static String traitDiff(RelTraitSet original, RelTraitSet desired) {
           .collect(Collectors.joining(", ", "[", "]"));
     }
 
-    public RelNode visit(
-        RelNode p,
-        int ordinal,
-        @Nullable RelNode parent) {
+    public RelNode visit(RelNode p,  int ordinal) {
+      return visit(p,ordinal,0);
+    }
+
+    private RelNode visit(RelNode p, int ordinal, int depth) {
       final int pId = p.getId();
       RelNode prevVisit = visited.get(pId);
       if (prevVisit != null) {
         // return memoized result of previous visit if available
         return prevVisit;
       }
 
+      if ( depth > 256) {
+        throw new RuntimeException("Cyclic relation graph detected at " + p);
+      }
+
       if (p instanceof RelSubset) {
         RelSubset subset = (RelSubset) p;
         RelNode cheapest = subset.best;
@@ -737,7 +742,7 @@ public RelNode visit(
       List<RelNode> inputs = new ArrayList<>();
       for (int i = 0; i < oldInputs.size(); i++) {
         RelNode oldInput = oldInputs.get(i);
-        RelNode input = visit(oldInput, i, p);
+        RelNode input = visit(oldInput, i, depth+1);
         inputs.add(input);
       }
       if (!inputs.equals(oldInputs)) {