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From "Vikas Saurabh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-3372) Collapsing external events in BackgroundObserver even before queue is full leads to JournalEntry not getting used
Date Wed, 09 Sep 2015 10:16:45 GMT

    [ https://issues.apache.org/jira/browse/OAK-3372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14736614#comment-14736614
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Vikas Saurabh commented on OAK-3372:
------------------------------------

bq. Those would then end up doing a lot of expensive extra diffs. 
Yes, I thought about them but the 'lot of' qualifier comes only when there was no local event
before 2 (or more) background reads that generate those external events. I felt that probability
of such cases is fairly low - thereby reducing the number of extra diffs that would be required.
In any case, we might want to do it only if journal based diff gets used (document based stuff
for now)...

> Collapsing external events in BackgroundObserver even before queue is full leads to JournalEntry
not getting used
> -----------------------------------------------------------------------------------------------------------------
>
>                 Key: OAK-3372
>                 URL: https://issues.apache.org/jira/browse/OAK-3372
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.3.5
>            Reporter: Vikas Saurabh
>              Labels: resilience
>
> BackgroundObserver currently merges external events if the last one in queue is also
an external event. This leads to diff being done for a revision pair which is different from
the ones pushed actively into cache during backgroud read (using JournalEntry) i.e. diff queries
for {{diff("/a/b", rA, rC)}} while background read had pushed results of {{diff("/a/b", rA,
rB)}} and {{diff("/a/b", rB, rC)}}.
> (cc [~mreutegg], [~egli], [~chetanm], [~mduerig])



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