[jira] [Commented] (OAK-3603) Evaluate skipping cleanup of a subset of tar files

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

    [ https://issues.apache.org/jira/browse/OAK-3603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14996622#comment-14996622 ] 

Alex Parvulescu commented on OAK-3603:
--------------------------------------

this depends on a stable set or referenced ids, so we'd need to fix OAK-3602 first.

> Evaluate skipping cleanup of a subset of tar files
> --------------------------------------------------
>
>                 Key: OAK-3603
>                 URL: https://issues.apache.org/jira/browse/OAK-3603
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: segmentmk
>            Reporter: Alex Parvulescu
>            Assignee: Alex Parvulescu
>
> Given the fact that tar readers are immutable (we only create new generations of them once they reach a certain threshold of garbage) we can consider coming up with a heuristic for skipping cleanup entirely for consequent cleanup calls based on the same referenced id set (provided we can make this set more stable, aka. OAK-2849).
> Ex: for a specific input set a cleanup call on a tar reader might decide that there's no enough garbage (some IO involved in reading through all existing entries). if the following cleanup cycle would have the exact same input, it doesn't make sense to recheck the tar file, we already know cleanup can be skipped, moreover we can skip the older tar files too, as their input would also not change. the gains increase the larger the number of tar files.



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