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From "Alex Parvulescu (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (OAK-3362) Estimate compaction based on diff to previous compacted head state
Date Fri, 25 Sep 2015 12:33:04 GMT

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

Alex Parvulescu reassigned OAK-3362:

    Assignee: Alex Parvulescu

> 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: Sub-task
>          Components: segmentmk
>            Reporter: Alex Parvulescu
>            Assignee: Alex Parvulescu
>            Priority: Minor
>              Labels: compaction, gc
>             Fix For: 1.3.8
> 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
> * 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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