[jira] [Resolved] (OAK-3362) Estimate compaction based on diff to previous compacted head state

["Alex Parvulescu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/OAK-3362?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alex Parvulescu resolved OAK-3362.
----------------------------------
       Resolution: Won't Fix
    Fix Version/s:     (was: Segment Tar 0.0.4)
                       (was: 1.6)

resolving as 'won't fix', based on comments. OAK-4293 will probably be the way to go.

> Estimate compaction based on diff to previous compacted head state
> ------------------------------------------------------------------
>
>                 Key: OAK-3362
>                 URL: https://issues.apache.org/jira/browse/OAK-3362
>             Project: Jackrabbit Oak
>          Issue Type: New Feature
>          Components: segment-tar
>            Reporter: Alex Parvulescu
>            Assignee: Alex Parvulescu
>            Priority: Minor
>              Labels: compaction, gc
>
> Food for thought: try to base the compaction estimation on a diff between the latest compacted state and the current state.
> Pros
> * estimation duration would be proportional to number of changes on the current head state
> * using the size on disk as a reference, we could actually stop the estimation early when we go over the gc threshold.
> * data collected during this diff could in theory be passed as input to the compactor so it could focus on compacting a specific subtree
> Cons
> * need to keep a reference to a previous compacted state. post-startup and pre-compaction this might prove difficult (except maybe if we only persist the revision similar to what the async indexer is doing currently)
> * coming up with a threshold for running compaction might prove difficult
> * diff might be costly, but still cheaper than the current full diff



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