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https://issues.apache.org/jira/browse/PHOENIX-418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16148175#comment-16148175
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Hadoop QA commented on PHOENIX-418:
-----------------------------------
{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12884517/PHOENIX-418-v6-pom.patch
against master branch at commit e6c1f01c5f7d5c9996017714efe90202a95355b2.
ATTACHMENT ID: 12884517
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+0 tests included{color}. The patch appears to be a
documentation, build,
or dev patch that doesn't require tests.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:red}-1 javadoc{color}. The javadoc tool appears to have generated
62 warning messages.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 lineLengths{color}. The patch does not introduce lines
longer than 100
{color:red}-1 core tests{color}. The patch failed these unit tests:
./phoenix-core/target/failsafe-reports/TEST-org.apache.phoenix.end2end.index.MutableIndexFailureIT
./phoenix-core/target/failsafe-reports/TEST-org.apache.phoenix.end2end.GroupByIT
./phoenix-core/target/failsafe-reports/TEST-org.apache.phoenix.end2end.TableSnapshotReadsMapReduceIT
Test results:
https://builds.apache.org/job/PreCommit-PHOENIX-Build/1325//testReport/
Javadoc warnings:
https://builds.apache.org/job/PreCommit-PHOENIX-Build/1325//artifact/patchprocess/patchJavadocWarnings.txt
Console output:
https://builds.apache.org/job/PreCommit-PHOENIX-Build/1325//console
This message is automatically generated.
> Support approximate COUNT DISTINCT
> ----------------------------------
>
> Key: PHOENIX-418
> URL: https://issues.apache.org/jira/browse/PHOENIX-418
> Project: Phoenix
> Issue Type: New Feature
> Reporter: James Taylor
> Assignee: Ethan Wang
> Priority: Blocker
> Labels: gsoc2016
> Fix For: 4.12.0
>
> Attachments: PHOENIX-418-v1.patch, PHOENIX-418-v2.patch,
> PHOENIX-418-v3.patch, PHOENIX-418-v4.patch, PHOENIX-418-v5.patch,
> PHOENIX-418-v6.patch, PHOENIX-418-v6-pom.patch
>
>
> Support an "approximation" of count distinct to prevent having to hold on to
> all distinct values (since this will not scale well when the number of
> distinct values is huge). The Apache Drill folks have had some interesting
> discussions on this
> [here](http://mail-archives.apache.org/mod_mbox/incubator-drill-dev/201306.mbox/%3CJIRA.12650169.1369931282407.88049.1370645900553%40arcas%3E).
> They recommend using [Welford's
> method](http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance_Online_algorithm).
> I'm open to having a config option that uses exact versus approximate. I
> don't have experience implementing an approximate implementation, so I'm not
> sure how much state is required to keep on the server and return to the
> client (other than realizing it'd be much less that returning all distinct
> values and their counts).
> Update:
> Syntax of using approximate count distinct as:
> select APPROX_COUNT_DISTINCT(name) from person
> select APPROX_COUNT_DISTINCT(address||name) from person
> It is equivalent of Select COUNT(DISTINCT ID) from person. Implemented using
> hyperloglog, see discuss below.
> Source code patch link below, co-authorred with [~swapna]
> https://git-wip-us.apache.org/repos/asf?p=phoenix.git;a=commitdiff;h=d6381afc3af976ccdbb874d4458ea17b1e8a1d32
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