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From "Hive QA (Jira)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-22238) PK/FK selectivity estimation underscales estimations
Date Fri, 08 Nov 2019 08:03:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-22238?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16969923#comment-16969923
] 

Hive QA commented on HIVE-22238:
--------------------------------



Here are the results of testing the latest attachment:
https://issues.apache.org/jira/secure/attachment/12985234/HIVE-22238.10.patch

{color:red}ERROR:{color} -1 due to build exiting with an error

Test results: https://builds.apache.org/job/PreCommit-HIVE-Build/19344/testReport
Console output: https://builds.apache.org/job/PreCommit-HIVE-Build/19344/console
Test logs: http://104.198.109.242/logs/PreCommit-HIVE-Build-19344/

Messages:
{noformat}
Executing org.apache.hive.ptest.execution.TestCheckPhase
Tests exited with: Exception: Patch URL https://issues.apache.org/jira/secure/attachment/12985234/HIVE-22238.10.patch
was found in seen patch url's cache and a test was probably run already on it. Aborting...
{noformat}

This message is automatically generated.

ATTACHMENT ID: 12985234 - PreCommit-HIVE-Build

> PK/FK selectivity estimation underscales estimations
> ----------------------------------------------------
>
>                 Key: HIVE-22238
>                 URL: https://issues.apache.org/jira/browse/HIVE-22238
>             Project: Hive
>          Issue Type: Bug
>          Components: Statistics
>            Reporter: Zoltan Haindrich
>            Assignee: Zoltan Haindrich
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: HIVE-22238.01.patch, HIVE-22238.02.patch, HIVE-22238.03.patch, HIVE-22238.04.patch,
HIVE-22238.05.patch, HIVE-22238.05.patch, HIVE-22238.05.patch, HIVE-22238.05.patch, HIVE-22238.05.patch,
HIVE-22238.06.patch, HIVE-22238.06.patch, HIVE-22238.07.patch, HIVE-22238.09.patch, HIVE-22238.10.patch,
HIVE-22238.10.patch, HIVE-22238.10.patch, HIVE-22238.10.patch
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> at [this point|https://github.com/apache/hive/blob/5098d155a1e6a164253f5fa98755273bc34085df/ql/src/java/org/apache/hadoop/hive/ql/optimizer/stats/annotation/StatsRulesProcFactory.java#L2182]
the parent operators rownum is scaled according to pkfkselectivity
> however [pkfkselectivity is computed|https://github.com/apache/hive/blob/5098d155a1e6a164253f5fa98755273bc34085df/ql/src/java/org/apache/hadoop/hive/ql/optimizer/stats/annotation/StatsRulesProcFactory.java#L2157]
on a whole subtree.
> Scaling it by that amount will count in estimation already used when parentstats was
calculated...so depending on the number of upstream joins - this may lead to severe underestimations
> what happened was:
> * optimization was able to push the filter to the other side of the join
> * as a result the incoming data was already filtered
> * scaling down by the PK selectiviy - was actually already there...but a new "scaling"
happened



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