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https://issues.apache.org/jira/browse/OAK-591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13576645#comment-13576645
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Jukka Zitting commented on OAK-591:
-----------------------------------
bq. If that's the case the KernelNodeStates have to track the initial read
revision of the root node state to have a fallback when there is no hash or id
later. But this again introduces data into the KernelNodeState, which changes
with every modification to the repository.
Hmm, good point. We could use something like {:id|:hash}path/to/subtree syntax
to identify nodes in such subtrees. Or simply require that a MK that returns an
:id or :hash for one node must do so also for all nodes in the subtree below
it. That should be easy enough to implement with such a partial path syntax if
hashes or other identifiers are not available.
> Improve KernelNodeStore cache efficiency
> ----------------------------------------
>
> Key: OAK-591
> URL: https://issues.apache.org/jira/browse/OAK-591
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: core
> Affects Versions: 0.6
> Reporter: Marcel Reutegger
> Attachments: mk.log.gz, OAK-591.patch
>
>
> The cache in KernelNodeStore references entries with a path+revision combo.
> This mapping quickly becomes inefficient when there are writes on the
> repository. Whenever something is changed, the complete cache basically
> becomes invalid and oak-core needs to re-fetch nodes again, even though they
> didn't change. The attached test shows this behaviour. The test initially
> creates 10 nodes and lets a thread read those nodes repeatedly. To make the
> test somewhat realistic the reader acquires a new session in every run
> through the loop. This is to simulate e.g. a request which acquires a new
> session every time (Apache Sling does it that way). At the same time writes
> occur but in a separate part of the repository. As can be seen in the logs,
> the nodes are read from the MicroKernel whenever something changes anywhere
> in the repository. Obviously this is no limited to the test nodes. The log
> also shows repeated reads to node type, user and index nodes. None of them
> change while the test runs.
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