[LUCENE-5805] QueryNodeImpl.removeFromParent does a lot of work without any effect

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.7.2, 4.9
• Fix Version/s: 5.3, 6.0
• Component/s: modules/queryparser
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Christoph Kaser
• Created: 04/Jul/14 11:56
• Updated: 28/Aug/22 14:11
• Resolved: 05/Jun/15 19:34

Description

The method removeFromParent of QueryNodeImpl, calls getChildren on the parent and removes any occurrence of "this" from the result.

However, since a few releases, getChildren returns a copy of the children list, so the code has no effect (except creating a copy of the children list which will then be thrown away).
Even worse, since setChildren calls removeFromParent on any previous child, setChildren now has a complexity of O(n^2) and creates a lot of throw-away copies of the children list (for nodes with a lot of children)

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;
    }
  }

Issue Links

• is duplicated by: LUCENE-6865 BooleanQuery2ModifierNodeProcessor breaks the query node hierarchy