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https://issues.apache.org/jira/browse/OAK-3070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15899605#comment-15899605
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Marcel Reutegger commented on OAK-3070:
---------------------------------------
I think the margin was introduced because of how
{{VersionGCSupport.getPossiblyDeletedDocs()}} compares the two timestamps. With
the patch, the garbage collector may miss some documents. Consider the
following GC runs with the patch:
Initially {{getPossiblyDeletedDocs()}} will return {{0 > getModifiedInSecs(doc)
<= t1}}. In the subsequent run it will return {{t1 > getModifiedInSecs(doc) <=
t2}}. There may be documents modified after t1 that still fall into the same 5
second resolution bucket as t1. The second run will not match them.
I'll update the issue with a new patch...
> Use a lower bound in VersionGC query to avoid checking unmodified once
> deleted docs
> -----------------------------------------------------------------------------------
>
> Key: OAK-3070
> URL: https://issues.apache.org/jira/browse/OAK-3070
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: mongomk, rdbmk
> Reporter: Chetan Mehrotra
> Assignee: Vikas Saurabh
> Labels: performance
> Attachments: OAK-3070.patch, OAK-3070-updated.patch,
> OAK-3070-updated.patch
>
>
> As part of OAK-3062 [~mreutegg] suggested
> {quote}
> As a further optimization we could also limit the lower bound of the _modified
> range. The revision GC does not need to check documents with a _deletedOnce
> again if they were not modified after the last successful GC run. If they
> didn't change and were considered existing during the last run, then they
> must still exist in the current GC run. To make this work, we'd need to
> track the last successful revision GC run.
> {quote}
> Lowest last validated _modified can be possibly saved in settings collection
> and reused for next run
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