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https://issues.apache.org/jira/browse/PHOENIX-4724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16469198#comment-16469198
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Maryann Xue commented on PHOENIX-4724:
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Yes, I agree with [~jamestaylor] that this information can be useful for the
query optimizer. Right now for WHERE clause conditions, other than those
filters on the primary key, we can only have a very rough "guess" of the number
of rows/bytes of the filtered output. This information can definitely give a
more accurate estimation for the filter conditions on columns covered by the
histogram. For example, for a range or equal condition on such columns, we can
estimate the filtered rows/bytes by calculating (number of buckets that fall in
the range / number of total buckets).
> Efficient Equi-Depth histogram for streaming data
> -------------------------------------------------
>
> Key: PHOENIX-4724
> URL: https://issues.apache.org/jira/browse/PHOENIX-4724
> Project: Phoenix
> Issue Type: Sub-task
> Affects Versions: 4.15.0
> Reporter: Vincent Poon
> Assignee: Vincent Poon
> Priority: Major
> Attachments: PHOENIX-4724.v1.patch, PHOENIX-4724.v2.patch
>
>
> Equi-Depth histogram from
> http://web.cs.ucla.edu/~zaniolo/papers/Histogram-EDBT2011-CamReady.pdf, but
> without the sliding window - we assume a single window over the entire data
> set.
> Used to generate the bucket boundaries of a histogram where each bucket has
> the same # of items.
> This is useful, for example, for pre-splitting an index table, by feeding in
> data from the indexed column.
> Works on streaming data - the histogram is dynamically updated for each new
> value.
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