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https://issues.apache.org/jira/browse/OAK-4412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15365939#comment-15365939
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Tomek Rękawek commented on OAK-4412:
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I'm quite happy with the current state of the patch and I'd like to merge it
into the trunk. My purpose was not to change any existing behaviour, but only
add a new feature, which has to be explicitly enabled (by using the
{{hybridIndex}} property in the index definition) - so this should be safe.
However, in order to introduce this new feature I had to change some of the
existing classes. Probably the most extensive changes are in the *IndexTracker*
(which now tracks the in-memory Lucene directories). The *LucenePropertyIndex*
has been changed as well, to return the union of results for the hybrid indices.
[~teofili], [~tmueller], [~catholicon], [~chetanm] - you are the main
contributors of the classes I'm modyfing. Could you take a look on the patch
and tell if it's acceptable? I'm planning to commit it on the Wednesday next
week.
> Lucene hybrid index
> -------------------
>
> Key: OAK-4412
> URL: https://issues.apache.org/jira/browse/OAK-4412
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: lucene
> Reporter: Tomek Rękawek
> Assignee: Tomek Rękawek
> Fix For: 1.6
>
> Attachments: OAK-4412.patch
>
>
> When running Oak in a cluster, each write operation is expensive. After
> performing some stress-tests with a geo-distributed Mongo cluster, we've
> found out that updating property indexes is a large part of the overall
> traffic.
> The asynchronous index would be an answer here (as the index update won't be
> made in the client request thread), but the AEM requires the updates to be
> visible immediately in order to work properly.
> The idea here is to enhance the existing asynchronous Lucene index with a
> synchronous, locally-stored counterpart that will persist only the data since
> the last Lucene background reindexing job.
> The new index can be stored in memory or (if necessary) in MMAPed local
> files. Once the "main" Lucene index is being updated, the local index will be
> purged.
> Queries will use an union of results from the {{lucene}} and
> {{lucene-memory}} indexes.
> The {{lucene-memory}} index, as a local stored entity, will be updated using
> an observer, so it'll get both local and remote changes.
> The original idea has been suggested by [~chetanm] in the discussion for the
> OAK-4233.
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