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https://issues.apache.org/jira/browse/HIVE-1397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12878808#action_12878808
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HBase Review Board commented on HIVE-1397:
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Message from: "John Sichi" <jsi...@facebook.com>
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This is an automatically generated e-mail. To reply, visit:
http://review.hbase.org/r/181/
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Review request for Hive Developers.
Summary
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Submitted on behalf of Mayank Lahiri.
This addresses bug HIVE-1397.
http://issues.apache.org/jira/browse/HIVE-1397
Diffs
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http://svn.apache.org/repos/asf/hadoop/hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/exec/FunctionRegistry.java
953449
http://svn.apache.org/repos/asf/hadoop/hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDAFHistogram.java
PRE-CREATION
http://svn.apache.org/repos/asf/hadoop/hive/trunk/ql/src/test/queries/clientpositive/udaf_histogram.q
PRE-CREATION
http://svn.apache.org/repos/asf/hadoop/hive/trunk/ql/src/test/results/clientpositive/show_functions.q.out
953449
http://svn.apache.org/repos/asf/hadoop/hive/trunk/ql/src/test/results/clientpositive/udaf_histogram.q.out
PRE-CREATION
Diff: http://review.hbase.org/r/181/diff
Testing
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None
Thanks,
John
> histogram() UDAF for a numerical column
> ---------------------------------------
>
> Key: HIVE-1397
> URL: https://issues.apache.org/jira/browse/HIVE-1397
> Project: Hadoop Hive
> Issue Type: New Feature
> Components: Query Processor
> Affects Versions: 0.6.0
> Reporter: Mayank Lahiri
> Assignee: Mayank Lahiri
> Fix For: 0.6.0
>
> Attachments: Histogram_quality.png.jpg, HIVE-1397.1.patch
>
>
> A histogram() UDAF to generate an approximate histogram of a numerical (byte,
> short, double, long, etc.) column. The result is returned as a map of (x,y)
> histogram pairs, and can be plotted in Gnuplot using impulses (for example).
> The algorithm is currently adapted from "A streaming parallel decision tree
> algorithm" by Ben-Haim and Tom-Tov, JMLR 11 (2010), and uses space
> proportional to the number of histogram bins specified. It has no
> approximation guarantees, but seems to work well when there is a lot of data
> and a large number (e.g. 50-100) of histogram bins specified.
> A typical call might be:
> SELECT histogram(val, 10) FROM some_table;
> where the result would be a histogram with 10 bins, returned as a Hive map
> object.
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