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https://issues.apache.org/jira/browse/ACCUMULO-227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13174469#comment-13174469
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Adam Fuchs commented on ACCUMULO-227:
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This is an extremely rare edge case, but not quite so rare that nobody has seen
it. By default, Accumulo tables use a versioning iterator that keeps the latest
version. Only keeping one of the values assigned to a given key within a
mutation preserves this behavior. However, when we configure a summing
aggregator on a table we would probably expect to see contributions from all of
the entries in a mutation, so the current behavior goes against our
expectations in that case. Aggregating on the client side would be one
solution, but that would involve a big change to the semantics of when and
where iterators run, as well as a lot of work building an iterator framework
that works on the client side. We already have the plumbing of supporting
multiple identical entries to support isolation. This is a rare enough problem
that performance will not be a concern, so I think the simple solution to this
particular problem is the one that is described.
> Improve in memory map counts to provide cell level uniqueness for repeated
> columns in mutation
> -----------------------------------------------------------------------------------------------
>
> Key: ACCUMULO-227
> URL: https://issues.apache.org/jira/browse/ACCUMULO-227
> Project: Accumulo
> Issue Type: Improvement
> Components: tserver
> Reporter: John Vines
> Assignee: John Vines
> Fix For: 1.5.0
>
>
> Currently for isolation we only isolate mutations. This doesn't allow
> mutations with identical cells within it. We should increase the mutation
> counts to account for each individual cell instead of each mutation.
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