[kudu-CR] design docs: Add tablet history GC design doc

["Mike Percy (Code Review)" <ge...@cloudera.org>]

Mike Percy has posted comments on this change.

Change subject: design docs: Add tablet history GC design doc
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Patch Set 4:

(6 comments)

http://gerrit.cloudera.org:8080/#/c/2853/4/docs/design-docs/tablet-history-gc.md
File docs/design-docs/tablet-history-gc.md:

PS4, Line 30: In the future
> I'm fine in design docs, I just think it's weird to see in a user doc.
I don't think it hurts in a design doc either. Leaving it unless I hear otherwise.


Line 38: unlinks an open block that has become ancient history.
> I think it's worth adding that Impala and Spark might have to run many scan
Done


Line 46: 1. The CompactRowSetsOp (merging compaction) tablet maintenance task.
> a little paragraph of text on how this removes old deltas on output would b
Done


Line 47: 2. The UndoDeltaBlockGCOp tablet maintenance task.
> worth describing this one somewhere (or a pointer to where it's described i
Done


PS4, Line 53: RowSets
> DiskRowSets*
Done


PS4, Line 61: In cases where a merging tablet compaction is not run, we still want to remove
            : old rows. We could implement a maintenance task specifically for GCing old
            : rows. However, at the time of writing, this is not implemented because it
            : appears to be prone to causing write amplification.
> think this could be clarified a little bit to contrast it to the UndoDeltaB
Done


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Gerrit-MessageType: comment
Gerrit-Change-Id: Ibd1776971ac4afa15a34daeced052913cf887dc3
Gerrit-PatchSet: 4
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Mike Percy <mp...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: Dan Burkert <da...@apache.org>
Gerrit-Reviewer: Jean-Daniel Cryans <jd...@apache.org>
Gerrit-Reviewer: Mike Percy <mp...@apache.org>
Gerrit-Reviewer: Todd Lipcon <to...@apache.org>
Gerrit-HasComments: Yes