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From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7842) Add compaction policy that explores more storefile groups
Date Fri, 29 Mar 2013 20:53:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7842?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13617708#comment-13617708

Elliott Clark commented on HBASE-7842:

bq.Interesting heuristic... it looks reasonable, but have you tried ratio proposed above?
E.g. getting rid of 3 files of 5Mb each is better than getting rid of 4 files of 500Mb each.
Yes the ratio proposed when this started has a tendency to get too stuck on small files.

bq.Double nested loop is unnecessary.
Removed that.  Though I didn't pass it in as the parameters should be instructive of usage
not just a performance optimization.

bq.Doesn't have to consider with less than minfiles to the end.

bq.Can go from start plus minfiles, and check maxfiles too, then checks inside become unnecessary...
Makes computing the end really ugly and for this loop it's easier to just use the continue.
 No harm in being more careful here.

> Add compaction policy that explores more storefile groups
> ---------------------------------------------------------
>                 Key: HBASE-7842
>                 URL: https://issues.apache.org/jira/browse/HBASE-7842
>             Project: HBase
>          Issue Type: New Feature
>          Components: Compaction
>            Reporter: Elliott Clark
>            Assignee: Elliott Clark
>         Attachments: HBASE-7842-0.patch, HBASE-7842-2.patch, HBASE-7842-3.patch, HBASE-7842-4.patch,
> Some workloads that are not as stable can have compactions that are too large or too
small using the current storefile selection algorithm.
> Currently:
> * Find the first file that Size(fi) <= Sum(0, i-1, FileSize(fx))
> * Ensure that there are the min number of files (if there aren't then bail out)
> * If there are too many files keep the larger ones.
> I would propose something like:
> * Find all sets of storefiles where every file satisfies 
> ** FileSize(fi) <= Sum(0, i-1, FileSize(fx))
> ** Num files in set =< max
> ** Num Files in set >= min
> * Then pick the set of files that maximizes ((# storefiles in set) / Sum(FileSize(fx)))
> The thinking is that the above algorithm is pretty easy reason about, all files satisfy
the ratio, and should rewrite the least amount of data to get the biggest impact in seeks.

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