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https://issues.apache.org/jira/browse/ACCUMULO-4500?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15588881#comment-15588881
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Josh Elser commented on ACCUMULO-4500:
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bq. we should limit the feature to be a mapping of names (type: String) to
counts (type: signed Long)
:coughs: That... is a histogram. Label (string) on x-axis, numeric value on the
y-axis. What is this aversion to using the word "histogram"? I honestly don't
understand the desire to avoid using that word.
bq. I think it would be a good idea that when this information is exposed in
the client API, it should be retrievable through a user-supplied
aggregation/combiner function
Can you sketch what you think this should look like? It's not entirely clear to
me.
bq. The reasoning for this is that client code doesn't normally deal with
things at the granularity of files, but rather, the granularity of tablets,
ranges, and tables
Keith had made a good point elsewhere that, when files overlap tablets, we
might double-count. That, combined with the counting (presently) not included
on the IMM, these "counters" (winks) would not be 100% accurate. Personally, I
think that's OK.
bq. A summation function would probably be the most common, but certainly not
the only useful aggregation function.
Example of another aggregation function?
> Implement visibility histograms as a table feature
> --------------------------------------------------
>
> Key: ACCUMULO-4500
> URL: https://issues.apache.org/jira/browse/ACCUMULO-4500
> Project: Accumulo
> Issue Type: New Feature
> Components: client, tserver
> Reporter: Josh Elser
>
> Add support to quickly extract a histogram of all of the visibilities stored
> in an Accumulo table.
> DISCUSS:
> https://lists.apache.org/thread.html/df5e764362a95277344fd2731a432e9fafc60595e7d30015d9a56b9c@%3Cdev.accumulo.apache.org%3E
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