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https://issues.apache.org/jira/browse/OAK-5212?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15722244#comment-15722244
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Chetan Mehrotra commented on OAK-5212:
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Thanks Vikas and Tommaso for the feedback.
bq. but I think the DirectoryReader#listCommits is slightly more expensive as
it requires IO (read)
Makes sense. I have improved the approach a bit to detect if some write has
happened via updateDocument call. In such case the generation based check is
avoided. As due to CoW reads here are local I would apply the patch as savings
on remote calls done to DocumentNodeStore would be good enough.
> Avoid updating the index nodestate if no change is done in index
> ----------------------------------------------------------------
>
> Key: OAK-5212
> URL: https://issues.apache.org/jira/browse/OAK-5212
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: lucene
> Reporter: Chetan Mehrotra
> Assignee: Chetan Mehrotra
> Priority: Minor
> Labels: performance
> Fix For: 1.6
>
> Attachments: OAK-5212-v1.patch
>
>
> As noted in OAK-5211 directory listing was getting modified (due to reorder)
> even if no change happens in index.
> Another place where we update state post index close is at ":status" node
> where we store {{lastUpdated}} and {{indexedNodes}} post index close. In
> normal cases LuceneIndexEditor avoids initializing the IndexWriter if there
> is no change. However it can happen that when any node gets deleted the
> editor performs a delete operation. It can happen that tree being deleted is
> not indexed but still editor would do this as it cannot determine that
> easily. And in doing that IndexWriter would be initialized.
> Currently IndexWriter being initialized is considered same as index updated.
> Due to this index status nodes gets unnecessarily updated even if there is no
> change in index which causes the IndexTracker to reopen the index even when
> it has not changed.
> We should make this more explicit and find a way to determine if index has
> been updated or not
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