Querying for shared nodes in JCR (ModeShape)

Question

I have a JCR content repository implemented in ModeShape (4.0.0.Final). The structure of the repository is quite simple and looks like this:

/ (root)
    Content/
        Item 1
        Item 2
        Item 3
        ...

    Tags/
        Foo/
        Bar/
        .../

The content is initially created and stored under /Content as [nt:unstructured] nodes with [mix:shareable] mixin. When a content item is tagged, the tag node is first created under /Tags if it's not already there, and the content node is shared/cloned to the tag node using Workspace.clone(...) as described in the JCR 2.0 spec, section 14.1, Creation of Shared Nodes.

(I don't find this particularly elegant and I did just read this answer, about creating a tag based search system in JCR, so I realize this might not be the best/fastest/most scaleable solution. But I "inherited" this solution from developers before me, so I hope I don't have to rewrite it all...)

Anyway, the sharing itself seems to work (I can verify that the nodes are there using the ModeShape Content Explorer web app or programatically by session.getRootNode().getNode("Tags/Foo").getNodes()). But I am not able to find any shared nodes using a query!

My initial try (using JCR_SQL2 syntax) was:

SELECT * FROM [nt:unstructured] AS content
    WHERE PATH(content) LIKE '/Tags/Foo/%' // ISDECENDANTNODE(content, '/Tags/Foo') gives same result
    ORDER BY NAME(content)

The result set was to my surprise empty.

I also tried searching in [mix:shareable] like this:

SELECT * FROM [mix:shareable] AS content
    WHERE PATH(content) LIKE '/Tags/Foo/%' // ISDECENDANTNODE(content, '/Tags/Foo') gives same result
    ORDER BY NAME(content)

This also returned an empty result set.

I can see from the query:

SELECT * FROM [nt:unstructured] AS content
    WHERE PATH(content) LIKE '/Content/%' // ISDECENDANTNODE(content, '/Content') works just as well
    ORDER BY NAME(content)

...that the query otherwise works, and returns the expected result (all content). It just doesn't work when searching for the shared nodes.

How do I correctly search for shared nodes in JCR using ModeShape?

Update: I upgraded to 4.1.0.Final to see if that helped, but it had no effect on the described behaviour.

I have posted the same question on the JBoss/ModeShape forums, due to lack of answers here. — Harald K

Randall Hauch Randall Hauch · Accepted Answer · 2015-02-13T14:35:35

Cross-posted from the ModeShape forum:

Shared nodes are really just a single node that appears in multiple places within a workspace, so it's not exactly clear what it semantically means to get multiple query results for that one shareable node. Per Section 14.16 of the JSR-283 (JCR 2.0) specification implementations are free to include shareable nodes in query results at just one or at multiple/all of those locations.

ModeShape 2.x and 3.x always returned in query results only a single location of the shared nodes, as this was the behavior of the reference implementation and this was the feedback we got from users. When we were working on Modeshape 4.0, we tried to make it possible to return multiple results, but we ran into problems with the TCK and uncertainty about what this new expected behavior would be. Therefore, we backed off our goals and implemented query to return only one of the shared locations, as we did with 2.x and 3.x.

I may be wrong, but I'm not exactly sure if any JCR implementation returns multiple rows for a single shared node, but I may be wrong.

Querying for shared nodes in JCR (ModeShape)

1 Answers