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From Michael Dürig (JIRA) <j...@apache.org>
Subject [jira] [Created] (OAK-3350) Imcremental compaction
Date Fri, 04 Sep 2015 09:00:52 GMT
Michael Dürig created OAK-3350:

             Summary: Imcremental compaction
                 Key: OAK-3350
                 URL: https://issues.apache.org/jira/browse/OAK-3350
             Project: Jackrabbit Oak
          Issue Type: Sub-task
          Components: segmentmk
            Reporter: Michael Dürig
            Assignee: Michael Dürig

This is OAK-3349 taken to the extreme: given a segment that is almost not referenced any more
we could just rewrite the still referenced content. That is, say a segment contains two properties
reachable from the current root node state and all its remaining content is not reachable
from the root node state. In that case we could rewrite these two properties and create a
new root node state referencing the rewritten properties. This would effectively make the
segment eligible for being gc-ed. 
Such an approach would start from segments that are sparse and compact these instead of compacting
everything as we currently do, which might cause a lot of copying around stuff that already
is compact. The challenging part here is probably finding the segments that are sparse as
this involves inverting the reference graph. 

Todo: Asses feasibility and impact, implement prototype.

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