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https://issues.apache.org/jira/browse/HBASE-4071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13084786#comment-13084786
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Lars Hofhansl commented on HBASE-4071:
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Having had a very brief look at the code it seems that wouldn't even be that
hard.
If we had (say) another CF attributes called "minversions", we could check for
that in ScanQueryMatcher.match(...) as such:
If minversions > 0 we'd still do the CF expiry check (isExpired), but instead
of bailing right there, we'd remember the resulting MatchCode, and continue all
the way to checkColumn(...) of the ColumnTracker. checkColumn would receive the
MatchCode from the expiry check as additional argument. Deletes and filters
should still behave correctly as far as I can see.
In ColumnTracker.checkColumn we now have three cases:
1. # version < minversions: behave as if the version check was positive
2. minversions < # versions < maxversion: return whatever the CF expiry check
would have returned. (the details are probably a bit more tricky)
3. # versions > maxversions: same behavior as before.
> Data GC: Remove all versions > TTL EXCEPT the last written version
> ------------------------------------------------------------------
>
> Key: HBASE-4071
> URL: https://issues.apache.org/jira/browse/HBASE-4071
> Project: HBase
> Issue Type: New Feature
> Reporter: stack
>
> We were chatting today about our backup cluster. What we want is to be able
> to restore the dataset from any point of time but only within a limited
> timeframe -- say one week. Thereafter, if the versions are older than one
> week, rather than as we do with TTL where we let go of all versions older
> than TTL, instead, let go of all versions EXCEPT the last one written. So,
> its like versions==1 when TTL > one week. We want to allow that if an error
> is caught within a week of its happening -- user mistakenly removes a
> critical table -- then we'll be able to restore up the the moment just before
> catastrophe hit otherwise, we keep one version only.
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