[CALCITE-5832] Avoid cycle in relational nodes.

sap-contributions · Dec 13, 2023 · 5cbd2dd · 5cbd2dd
1 parent a6729b7
commit 5cbd2dd
Showing 1 changed file with 44 additions and 18 deletions.
diff --git a/core/src/main/java/org/apache/calcite/plan/volcano/VolcanoPlanner.java b/core/src/main/java/org/apache/calcite/plan/volcano/VolcanoPlanner.java
@@ -70,17 +70,7 @@
 
 import java.io.PrintWriter;
 import java.io.StringWriter;
-import java.util.ArrayDeque;
-import java.util.ArrayList;
-import java.util.Deque;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.IdentityHashMap;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.PriorityQueue;
-import java.util.Set;
+import java.util.*;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -1107,13 +1097,17 @@ private boolean fixUpInputs(RelNode rel) {
       assert input instanceof RelSubset;
       final RelSubset subset = (RelSubset) input;
       RelSubset newSubset = canonize(subset);
-      newInputs.add(newSubset);
-      if (newSubset != subset) {
-        if (subset.set != newSubset.set) {
-          subset.set.parents.remove(rel);
-          newSubset.set.parents.add(rel);
+      if (hasCycle(rel,newSubset)) {
+        newInputs.add(input);
+      } else {
+        newInputs.add(newSubset);
+        if (newSubset != subset) {
+          if (subset.set != newSubset.set) {
+            subset.set.parents.remove(rel);
+            newSubset.set.parents.add(rel);
+          }
+          changeCount++;
         }
-        changeCount++;
       }
     }
 
@@ -1122,14 +1116,46 @@ private boolean fixUpInputs(RelNode rel) {
       RelNode removed = mapDigestToRel.remove(rel.getRelDigest());
       assert removed == rel;
       for (int i = 0; i < inputs.size(); i++) {
-        rel.replaceInput(i, newInputs.get(i));
+        RelNode newInput = newInputs.get(i);
+        rel.replaceInput(i, newInput);
       }
       rel.recomputeDigest();
       return true;
     }
     return false;
   }
 
+  private boolean hasCycle(RelNode rel, RelNode newInput) {
+    Stack<Integer> visited = new Stack<>();
+    visited.push(rel.getId());
+    return hasCycle(newInput,visited);
+  }
+
+  private boolean hasCycle(RelNode node, Stack<Integer> visited) {
+    if (node instanceof RelSubset) {
+      RelSubset subset = (RelSubset) node;
+      node = subset.getBestOrOriginal();
+    }
+    if ( visited.contains(node.getId()) ) {
+      return true;
+    }
+    try {
+      visited.push(node.getId());
+      List<RelNode> inputs = node.getInputs();
+      for (RelNode input : inputs) {
+        boolean cycle = hasCycle(input, visited);
+        if ( cycle) {
+          return true;
+        }
+      }
+    } finally {
+      visited.pop();
+    }
+    return false;
+  }
+
+
+
   private RelSet merge(RelSet set1, RelSet set2) {
     assert set1 != set2 : "pre: set1 != set2";