Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 1558306)
+++ lucene/CHANGES.txt	(working copy)
@@ -34,6 +34,9 @@
   AnalyzingInfixSuggester but boosts suggestions that matched tokens
   with lower positions.  (Remi Melisson via Mike McCandless)
 
+* LUCENE-5099: QueryNode should have the ability to detach from its node
+  parent. Added QueryNode.removeFromParent() that allows nodes to be 
+  detached from its parent node. (Adriano Crestani)
 
 Build
 
Index: lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/QueryNode.java
===================================================================
--- lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/QueryNode.java	(revision 1558304)
+++ lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/QueryNode.java	(working copy)
@@ -91,4 +91,8 @@
    */
   public Map<String, Object> getTagMap();
 
+  /**
+   * Removes this query node from its parent.
+   */
+  public void removeFromParent();
 }
Index: lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/QueryNodeImpl.java
===================================================================
--- lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/QueryNodeImpl.java	(revision 1558304)
+++ lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/QueryNodeImpl.java	(working copy)
@@ -19,6 +19,7 @@
 
 import java.util.ArrayList;
 import java.util.Hashtable;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -102,18 +103,19 @@
 
     // reset parent value
     for (QueryNode child : children) {
-
-      ((QueryNodeImpl) child).setParent(null);
-
+      child.removeFromParent();
     }
-
+    
+    ArrayList<QueryNode> existingChildren = new ArrayList<QueryNode>(getChildren());
+    for (QueryNode existingChild : existingChildren) {
+      existingChild.removeFromParent();
+    }
+    
     // allocate new children list
     allocate();
-
+    
     // add new children and set parent
-    for (QueryNode child : children) {
-      add(child);
-    }
+    add(children);
   }
 
   @Override
@@ -154,7 +156,7 @@
     if (isLeaf() || this.clauses == null) {
       return null;
     }
-    return this.clauses;
+    return new ArrayList<QueryNode>(this.clauses);
   }
 
   @Override
@@ -181,7 +183,10 @@
   private QueryNode parent = null;
 
   private void setParent(QueryNode parent) {
-    this.parent = parent;
+    if (this.parent != parent) {
+      this.removeFromParent();
+      this.parent = parent;
+    }
   }
 
   @Override
@@ -241,5 +246,21 @@
   public Map<String, Object> getTagMap() {
     return (Map<String, Object>) this.tags.clone();
   }
+  
+  @Override
+  public void removeFromParent() {
+    if (this.parent != null) {
+      List<QueryNode> parentChildren = this.parent.getChildren();
+      Iterator<QueryNode> it = parentChildren.iterator();
+      
+      while (it.hasNext()) {
+        if (it.next() == this) {
+          it.remove();
+        }
+      }
+      
+      this.parent = null;
+    }
+  }
 
 } // end class QueryNodeImpl
Index: lucene/queryparser/src/test/org/apache/lucene/queryparser/flexible/core/nodes/TestQueryNode.java
===================================================================
--- lucene/queryparser/src/test/org/apache/lucene/queryparser/flexible/core/nodes/TestQueryNode.java	(revision 1558304)
+++ lucene/queryparser/src/test/org/apache/lucene/queryparser/flexible/core/nodes/TestQueryNode.java	(working copy)
@@ -18,6 +18,7 @@
  */
 
 import java.util.Arrays;
+import java.util.Collections;
 
 import org.apache.lucene.util.LuceneTestCase;
 
@@ -44,4 +45,23 @@
     
   }
   
+  /* LUCENE-5099 - QueryNodeProcessorImpl should set parent to null before returning on processing */
+  public void testRemoveFromParent() throws Exception {
+    BooleanQueryNode booleanNode = new BooleanQueryNode(Collections.<QueryNode>emptyList());
+    FieldQueryNode fieldNode = new FieldQueryNode("foo", "A", 0, 1);
+    assertNull(fieldNode.getParent());
+    
+    booleanNode.add(fieldNode);
+    assertNotNull(fieldNode.getParent());
+
+    fieldNode.removeFromParent();
+    assertNull(fieldNode.getParent());
+
+    booleanNode.add(fieldNode);
+    assertNotNull(fieldNode.getParent());
+    
+    booleanNode.set(Collections.<QueryNode>emptyList());
+    assertNull(fieldNode.getParent());
+  }
+  
 }
Index: lucene/queryparser/src/test/org/apache/lucene/queryparser/util/QueryParserTestBase.java
===================================================================
--- lucene/queryparser/src/test/org/apache/lucene/queryparser/util/QueryParserTestBase.java	(revision 1558306)
+++ lucene/queryparser/src/test/org/apache/lucene/queryparser/util/QueryParserTestBase.java	(working copy)
@@ -1066,6 +1066,7 @@
     assertTrue(bq.getClauses()[1].getQuery() instanceof MatchAllDocsQuery);
   }
   
+  @SuppressWarnings("unused")
   private void assertHits(int expected, String query, IndexSearcher is) throws Exception {
     String oldDefaultField = getDefaultField();
     setDefaultField("date");