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https://issues.apache.org/jira/browse/HIVE-4435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13677850#comment-13677850
]
Hudson commented on HIVE-4435:
------------------------------
Integrated in Hive-trunk-h0.21 #2132 (See
[https://builds.apache.org/job/Hive-trunk-h0.21/2132/])
HIVE-4435 : Column stats: Distinct value estimator should use hash
functions that are pairwise independent (Shreepadma Venugopalan via Ashutosh
Chauhan) (Revision 1490323)
Result = FAILURE
hashutosh :
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1490323
Files :
*
/hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/udf/generic/NumDistinctValueEstimator.java
* /hive/trunk/ql/src/test/results/clientpositive/compute_stats_double.q.out
* /hive/trunk/ql/src/test/results/clientpositive/compute_stats_long.q.out
* /hive/trunk/ql/src/test/results/clientpositive/compute_stats_string.q.out
> Column stats: Distinct value estimator should use hash functions that are
> pairwise independent
> ----------------------------------------------------------------------------------------------
>
> Key: HIVE-4435
> URL: https://issues.apache.org/jira/browse/HIVE-4435
> Project: Hive
> Issue Type: Bug
> Components: Statistics
> Affects Versions: 0.10.0, 0.11.0
> Reporter: Shreepadma Venugopalan
> Assignee: Shreepadma Venugopalan
> Fix For: 0.12.0
>
> Attachments: chart_1(1).png, HIVE-4435.1.patch, HIVE-4435.2.patch
>
>
> The current implementation of Flajolet-Martin estimator to estimate the
> number of distinct values doesn't use hash functions that are pairwise
> independent. This is problematic because the input values don't distribute
> uniformly. When run on large TPC-H data sets, this leads to a huge
> discrepancy for primary key columns. Primary key columns are typically a
> monotonically increasing sequence.
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