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From "Marcel Reutegger (JIRA)" <j...@apache.org>
Subject [jira] [Created] (OAK-2562) DiffCache is inefficient
Date Tue, 03 Mar 2015 07:52:04 GMT
Marcel Reutegger created OAK-2562:

             Summary: DiffCache is inefficient
                 Key: OAK-2562
                 URL: https://issues.apache.org/jira/browse/OAK-2562
             Project: Jackrabbit Oak
          Issue Type: Bug
          Components: core, mongomk
    Affects Versions: 1.0
            Reporter: Marcel Reutegger
            Assignee: Marcel Reutegger

The diffCache in DocumentNodeStore can be quite inefficient in some cases. It may become ineffective
even for rather recent commits.

The diffCache contains entries for changes of a commit. E.g. it may have an entry that says
between revision r7-0-1 and r8-0-1 the following happened under /foo: 'bar' was modified,
'baz' was added, etc. The problem now is, that the revision range in the diffCache refers
to the revision of the commit and its base version, whereas on runtime, the diff calls may
likely happen for other revision ranges. The further down the tree the node state comparison
happens, the more likely it is that the base state has a different revision than the entry
in the cache. The DocumentNodeStore attempts to 'link' node states back in time to avoid reading
the complete tree at a different revision after each commit.

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