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https://issues.apache.org/jira/browse/OAK-1907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14231199#comment-14231199
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Michael Dürig commented on OAK-1907:
------------------------------------
[~tmueller] the changes from http://svn.apache.org/r1642683 break the test
expectations of {{ObservationRefreshTest#observation}} thus causing it to fail.
That test doesn't expect events for
{code}
/oak:index/counter/reindexCount
/oak:index/counter/reindex
{code}
I updated the test expectations at http://svn.apache.org/r1642825. However,
such additional events might as well also affect existing applications so I'm
nor sure whether this is really what we want.
> Better cost estimates for traversal, property, and ordered indexes
> ------------------------------------------------------------------
>
> Key: OAK-1907
> URL: https://issues.apache.org/jira/browse/OAK-1907
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: query
> Affects Versions: 1.0, 1.0.1, 1.0.2
> Reporter: Thomas Mueller
> Assignee: Thomas Mueller
> Fix For: 1.2
>
> Attachments: ApproxCount.java, OAK-1907.diff
>
>
> Currently, cost estimates of traversal, property index, and ordered index
> don't take the number of nodes into account, if there are more than about 100
> nodes. This is problematic because in many cases, the wrong index is used
> (because of incorrect cost estimate).
> To get a better estimate, a very rough estimate on the number of child nodes
> below a given path is needed.
> One idea is: when adding a node, if Math.random() < 0.00001, add a hidden,
> randomly named property (for example called ":count-xyz" where xyz is a uuid,
> value 100'000) to the parents of that node, so that we know there are
> probably more than 100'000 nodes below a given path. When removing a node,
> with the same algorithm add a hidden property (":count-xyz", value -100'000).
> That should result in a slowdown of less than 0.01%, but should allow us much
> better cost estimates. Those properties could be consolidated asynchronously
> if needed.
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