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https://issues.apache.org/jira/browse/HBASE-2406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12893234#action_12893234
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stack commented on HBASE-2406:
------------------------------
Here is one from this morning:
{code}
08:49 < paul> i put a value on row x, cf y, col z, ts 0 with value 1 then I put
row x, cf y, col z, ts 1 with value 2. if i scan or get {VERSIONS=>5} (from
shell)
I get value 2, but if I scan {TIMESTAMP=>0) I still get value 1
back even though I should not exist...
08:49 < paul> *it
...
09:12 < St^Ack> paul: which version of hbase?
09:13 < paul> latest stable i think (shell reports 0.20.5 for VERSION)
09:17 < St^Ack> paul: why would value 1 not exist?
09:17 < St^Ack> you expect that because you set versions == 1, that it should
suppress return of value 1
09:17 < St^Ack> ?
09:17 < paul> i assumed (possibly naievely) that because it only keeps one
version and as value 2 has a newer timestamp that yes, i thought it would?
09:18 < paul> is that entirely wrong?
09:18 < St^Ack> paul: its not how it works
09:18 < St^Ack> as to whether you are 'wrong', I'd say you are not -- your
expectation makes sense
09:18 < paul> oh right thanks :), so what happens to older versions? do they go
eventually or just waste space?
09:19 < St^Ack> they go eventually
09:19 < tlipcon> it will work after a major compaction
{code}
> Define semantics of cell timestamps/versions
> --------------------------------------------
>
> Key: HBASE-2406
> URL: https://issues.apache.org/jira/browse/HBASE-2406
> Project: HBase
> Issue Type: Task
> Components: documentation
> Reporter: Todd Lipcon
> Priority: Critical
> Fix For: 0.90.0
>
>
> There is a lot of general confusion over the semantics of the cell timestamp.
> In particular, a couple questions that often come up:
> - If multiple writes to a cell have the same timestamp, are all versions
> maintained or just the last?
> - Is it OK to write cells in a non-increasing timestamp order?
> Let's discuss, figure out what semantics make sense, and then move towards
> (a) documentation, (b) unit tests that prove we have those semantics.
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