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https://issues.apache.org/jira/browse/OAK-1389?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Mueller resolved OAK-1389.
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Resolution: Fixed
Revision 1565301 (test case)
> Query: an index is used even where traversing is faster
> -------------------------------------------------------
>
> Key: OAK-1389
> URL: https://issues.apache.org/jira/browse/OAK-1389
> Project: Jackrabbit Oak
> Issue Type: Bug
> Components: query
> Reporter: Thomas Mueller
> Assignee: Thomas Mueller
> Fix For: 0.17
>
>
> Currently, for queries that can use an index, the index is always preferred
> over traversing over the nodes. For joins, sometimes is much faster to
> traverse, specially the exact path is known. Example:
> {noformat}
> /jcr:root/testroot/node[@jcr:uuid]
> {noformat}
> This query will use the index on "jcr:uuid", and traverse over all nodes with
> the property "jcr:uuid", even thought in fact only one node would need to be
> read when using the TraversingIndex.
> The problems are: Currently, the TraversingIndex is not even asked to
> estimate the cost. Also, the cost estimation of the TraversingIndex is
> incorrect for such cases.
> We will also need to verify and fix the cost estimation of the other indexes
> (for example the PropertyIndex) conforms the QueryIndex API (getCost is
> supposed to return the estimated number of entries to traverse).
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