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

["Christoph Kaser (JIRA)" <ji...@apache.org>]

Christoph Kaser created LUCENE-5805:
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             Summary: QueryNodeImpl.removeFromParent does a lot of work without any effect
                 Key: LUCENE-5805
                 URL: https://issues.apache.org/jira/browse/LUCENE-5805
             Project: Lucene - Core
          Issue Type: Bug
          Components: modules/queryparser
    Affects Versions: 4.9, 4.7.2
            Reporter: Christoph Kaser


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 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)

{code]
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;
    }
  }
{code}



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