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https://issues.apache.org/jira/browse/HBASE-4536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13128355#comment-13128355
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Lars Hofhansl commented on HBASE-4536:
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Fair enough. Was picking up on Stack's suggestion to have this on by default.
Just means the code has to distinguish between minor and major compaction
scans, raw scans, and normal user scans, all of which can be for a store with
keep_delete_cells enabled or not.
Thinking about a ScanConfig (or ScanInfo) as static inner class of Store. That
would capture all immutable scan-relevant information about the Store (min/max
version, family name, ttl, keep_deletes, comparator). (A MatcherConfig with all
information would need to be mutable and created or changed for every scan.)
And then maybe a ScanType enum to distinguish between compaction scans and user
initiated scans.
What about Stack's suggested in the review to include delete cells in the
version count? (The only strange part with that is that the family markers are
*always* in the beginning).
Right now a delete cell does not increase the version count and instead
"inherits" the version of the last put.
> Allow CF to retain deleted rows
> -------------------------------
>
> Key: HBASE-4536
> URL: https://issues.apache.org/jira/browse/HBASE-4536
> Project: HBase
> Issue Type: New Feature
> Components: regionserver
> Affects Versions: 0.92.0
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Fix For: 0.94.0
>
>
> Parent allows for a cluster to retain rows for a TTL or keep a minimum number
> of versions.
> However, if a client deletes a row all version older than the delete tomb
> stone will be remove at the next major compaction (and even at memstore flush
> - see HBASE-4241).
> There should be a way to retain those version to guard against software error.
> I see two options here:
> 1. Add a new flag HColumnDescriptor. Something like "RETAIN_DELETED".
> 2. Folds this into the parent change. I.e. keep minimum-number-of-versions of
> versions even past the delete marker.
> #1 would allow for more flexibility. #2 comes somewhat naturally with parent
> (from a user viewpoint)
> Comments? Any other options?
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