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https://issues.apache.org/jira/browse/OAK-4780?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15875870#comment-15875870
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Julian Reschke commented on OAK-4780:
-------------------------------------

Here's an approach that might be simpler but in the end achieves the same goal:

- set a limit for the collection phase, both for elapsed time and # of documents
- when limit reached, sort the collected IDs by modified date, and compute a 
new upper limit so that half of the documents become out of range; throw these 
entries as well
- continue the collection with the smaller time window (this just needs an 
internal API that allows to specify the _id to start with)
- compute new limit for elapsed time (half of the original?)

Eventually, we should have a set of documents that we *can* garbage collect.

Finally, if maintenance window still open, just rerun the GC again.

> VersionGarbageCollector should be able to run incrementally
> -----------------------------------------------------------
>
>                 Key: OAK-4780
>                 URL: https://issues.apache.org/jira/browse/OAK-4780
>             Project: Jackrabbit Oak
>          Issue Type: Task
>          Components: core, documentmk
>            Reporter: Julian Reschke
>         Attachments: leafnodes.diff, leafnodes-v2.diff, leafnodes-v3.diff
>
>
> Right now, the documentmk's version garbage collection runs in several phases.
> It first collects the paths of candidate nodes, and only once this has been 
> successfully finished, starts actually deleting nodes.
> This can be a problem when the regularly scheduled garbage collection is 
> interrupted during the path collection phase, maybe due to other maintenance 
> tasks. On the next run, the number of paths to be collected will be even 
> bigger, thus making it even more likely to fail.
> We should think about a change in the logic that would allow the GC to run in 
> chunks; maybe by partitioning the path space by top level directory.



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