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From "Serge Huber (JIRA)" <j...@apache.org>
Subject [jira] Created: (JCR-2835) Poor performance of ISDESCENDANTNODE on SQL 2 queries
Date Wed, 08 Dec 2010 07:39:01 GMT
Poor performance of ISDESCENDANTNODE on SQL 2 queries
-----------------------------------------------------

                 Key: JCR-2835
                 URL: https://issues.apache.org/jira/browse/JCR-2835
             Project: Jackrabbit Content Repository
          Issue Type: Bug
    Affects Versions: 2.2.0
            Reporter: Serge Huber



Using the latest source code, I have noticed very bad performance on SQL-2 queries that use
the ISDESCENDANTNODE constraint on a large sub-tree. For example, the query : 

select * from [jnt:news] as news where ISDESCENDANTNODE(news,'/root/site') order by news.[date]
desc 

executes in 600ms 

select * from [jnt:news] as news order by news.[date] desc

executes in 4ms

>From looking at the problem in the Yourkit profiler, it seems that the culprit is the
constraint building, that uses recursive Lucene searches to build the list of descendant node
IDs : 

    private Query getDescendantNodeQuery(
            DescendantNode dn, JackrabbitIndexSearcher searcher)
            throws RepositoryException, IOException {
        BooleanQuery query = new BooleanQuery();

        try {
            LinkedList<NodeId> ids = new LinkedList<NodeId>();
            NodeImpl ancestor = (NodeImpl) session.getNode(dn.getAncestorPath());
            ids.add(ancestor.getNodeId());
            while (!ids.isEmpty()) {
                String id = ids.removeFirst().toString();
                Query q = new JackrabbitTermQuery(new Term(FieldNames.PARENT, id));
                QueryHits hits = searcher.evaluate(q);
                ScoreNode sn = hits.nextScoreNode();
                if (sn != null) {
                    query.add(q, SHOULD);
                    do {
                        ids.add(sn.getNodeId());
                        sn = hits.nextScoreNode();
                    } while (sn != null);
                }
            }
        } catch (PathNotFoundException e) {
            query.add(new JackrabbitTermQuery(new Term(
                    FieldNames.UUID, "invalid-node-id")), // never matches
                    SHOULD);
        }

        return query;
    }

In the above example this generates over 2800 Lucene queries, which is the culprit. I wonder
if it wouldn't be faster to retrieve the IDs by using the JCR to retrieve the list of child
IDs ?

This was probably also missed because I didn't seem to find any performance tests on this
constraint.

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