Poor performance of ISDESCENDANTNODE on SQL 2 queries
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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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