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From "Serge Huber (JIRA)" <j...@apache.org>
Subject [jira] Updated: (JCR-2835) Poor performance of ISDESCENDANTNODE on SQL 2 queries
Date Fri, 17 Dec 2010 07:36:01 GMT

     [ https://issues.apache.org/jira/browse/JCR-2835?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Serge Huber updated JCR-2835:
-----------------------------

    Attachment: SQL2DescendantSearchTest.png
                DescendantSearchTest.png

I have generated the performance graphs and indeed this patch looks really good !

Btw I had a lot of trouble generating the graphs under Mac OS X. It took me a while to understand
that I needed to install the following packages from fink : 

imagemagick2-svg
gnuplot

I think we might want to add that to the README.txt if there are others trying to use Mac
OS X to generate the graphs.

If nobody has any objections, I'd like to commit this patch since the results are really much
better ?

Best regards,
  Serge Huber.

> 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: Improvement
>          Components: jackrabbit-core, query
>    Affects Versions: 2.2.0, 2.2.1, 2.3.0
>            Reporter: Serge Huber
>             Fix For: 2.3.0
>
>         Attachments: DescendantSearchTest.png, JCR-2835-use-DescendantSelfAxisQuery.patch,
JCR-2835_PerformanceTests.patch, JCR-2835_Poor_performance_on_ISDESCENDANTNODE_constraint_v1.patch,
SQL2DescendantSearchTest.png
>
>
> 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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