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From "Hive QA (Jira)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-22238) PK/FK selectivity estimation underscales estimations
Date Mon, 21 Oct 2019 19:13:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-22238?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16956387#comment-16956387
] 

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

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|| Vote || Subsystem || Runtime || Comment ||
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| {color:green}+1{color} | {color:green} @author {color} | {color:green}  0m  0s{color} |
{color:green} The patch does not contain any @author tags. {color} |
|| || || || {color:brown} master Compile Tests {color} ||
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  8m 40s{color}
| {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m  6s{color} |
{color:green} master passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 41s{color}
| {color:green} master passed {color} |
| {color:blue}0{color} | {color:blue} findbugs {color} | {color:blue}  4m  8s{color} | {color:blue}
ql in master has 1547 extant Findbugs warnings. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  1m  2s{color} |
{color:green} master passed {color} |
|| || || || {color:brown} Patch Compile Tests {color} ||
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  1m 30s{color}
| {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m  9s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  1m  9s{color} | {color:green}
the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 41s{color}
| {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} whitespace {color} | {color:green}  0m  0s{color}
| {color:green} The patch has no whitespace issues. {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  4m 24s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  1m  2s{color} |
{color:green} the patch passed {color} |
|| || || || {color:brown} Other Tests {color} ||
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  0m 16s{color}
| {color:green} The patch does not generate ASF License warnings. {color} |
| {color:black}{color} | {color:black} {color} | {color:black} 26m  3s{color} | {color:black}
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|| Subsystem || Report/Notes ||
| Optional Tests |  asflicense  javac  javadoc  findbugs  checkstyle  compile  |
| uname | Linux hiveptest-server-upstream 3.16.0-4-amd64 #1 SMP Debian 3.16.43-2+deb8u5 (2017-09-19)
x86_64 GNU/Linux |
| Build tool | maven |
| Personality | /data/hiveptest/working/yetus_PreCommit-HIVE-Build-19091/dev-support/hive-personality.sh
|
| git revision | master / c9850b4 |
| Default Java | 1.8.0_111 |
| findbugs | v3.0.1 |
| modules | C: ql U: ql |
| Console output | http://104.198.109.242/logs//PreCommit-HIVE-Build-19091/yetus.txt |
| Powered by | Apache Yetus    http://yetus.apache.org |


This message was automatically generated.



> 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
>         Attachments: HIVE-22238.01.patch, HIVE-22238.02.patch, HIVE-22238.03.patch
>
>
> 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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