[jira] [Created] (OAK-530) Optimization for xpath queries of type "/jcr:root//*[x/@y]"

["Thomas Mueller (JIRA)" <ji...@apache.org>]

Thomas Mueller created OAK-530:
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             Summary: Optimization for xpath queries of type "/jcr:root//*[x/@y]"
                 Key: OAK-530
                 URL: https://issues.apache.org/jira/browse/OAK-530
             Project: Jackrabbit Oak
          Issue Type: Bug
          Components: query
            Reporter: Thomas Mueller
            Assignee: Thomas Mueller


Currently, the xpath query {{/jcr:root//*[x/@y]}} is converted to:

{code}
select [jcr:path], [jcr:score], * from [nt:base] as a
where [x/y] is not null
and isdescendantnode(a, '/')
{code}

This works well (the query is executed and returns the correct result as far as I understand), but currently no index is used, even if there is an index for the property {{y}}.

To speed up executing such queries, we could

(a) change the converter to convert to a different SQL-2 query so that an index is used, or

(b) implement a special 'virtual' index that internally uses a property index, and then returns the parent nodes instead of the node that contain the property.

Currently, I think (b) is simpler, so I will try that.

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