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https://issues.apache.org/jira/browse/HIVE-20660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16639972#comment-16639972
]
Hive QA commented on HIVE-20660:
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|| Vote || Subsystem || Runtime || Comment ||
|| || || || {color:brown} Prechecks {color} ||
| {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
26s{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
37s{color} | {color:green} master passed {color} |
| {color:blue}0{color} | {color:blue} findbugs {color} | {color:blue} 4m
5s{color} | {color:blue} ql in master has 2320 extant Findbugs warnings.
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| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 0m
58s{color} | {color:green} master passed {color} |
|| || || || {color:brown} Patch Compile Tests {color} ||
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 1m
28s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 1m
5s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green} 1m
5s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green} 0m
39s{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
18s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 0m
59s{color} | {color:green} the patch passed {color} |
|| || || || {color:brown} Other Tests {color} ||
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green} 0m
13s{color} | {color:green} The patch does not generate ASF License warnings.
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| {color:black}{color} | {color:black} {color} | {color:black} 24m 26s{color} |
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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
3.16.36-1+deb8u1 (2016-09-03) x86_64 GNU/Linux |
| Build tool | maven |
| Personality |
/data/hiveptest/working/yetus_PreCommit-HIVE-Build-14255/dev-support/hive-personality.sh
|
| git revision | master / f0434c5 |
| Default Java | 1.8.0_111 |
| findbugs | v3.0.0 |
| modules | C: ql U: ql |
| Console output |
http://104.198.109.242/logs//PreCommit-HIVE-Build-14255/yetus.txt |
| Powered by | Apache Yetus http://yetus.apache.org |
This message was automatically generated.
> Group by statistics estimation could be improved by bounding the total number
> of rows to source table
> -----------------------------------------------------------------------------------------------------
>
> Key: HIVE-20660
> URL: https://issues.apache.org/jira/browse/HIVE-20660
> Project: Hive
> Issue Type: Improvement
> Components: Statistics
> Affects Versions: 4.0.0
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Priority: Major
> Attachments: HIVE-20660.1.patch, HIVE-20660.2.patch,
> HIVE-20660.3.patch, HIVE-20660.4.patch
>
>
> Currently the stats for group by is estimated by taking product of NDVs of
> all the keys and bounding it by the number of rows of its input. This bound
> could be improved by using the source table instead of immediate input, the
> insight in this case is that cardinality/ndvs of a table can not go beyond
> the original (outer joins will only add NULLs thereby increasing the
> cardinality by 1).
> Note that the assumption here is that group by keys all belong to the same
> source table/input.
> This will improve the estimation in situations where group by is executed
> after joins wherein Hive could end up estimating the number of rows.
> *Reproducer*
> {code:sql}
> set hive.stats.fetch.column.stats=true;
> create table t1(i int, j int);
> alter table t1 update statistics set('numRows'='10000',
> 'rawDataSize'='18000');
> alter table t1 update statistics for column i
> set('numDVs'='2500','numNulls'='50','highValue'='1000','lowValue'='0');
> alter table t1 update statistics for column j
> set('numDVs'='500','numNulls'='30','highValue'='100','lowValue'='50');
> create table t2(i2 int, j2 int);
> alter table t2 update statistics set('numRows'='100000000',
> 'rawDataSize'='10000');
> alter table t2 update statistics for column i2
> set('numDVs'='10000000','numNulls'='0','highValue'='8000','lowValue'='0');
> alter table t2 update statistics for column j2
> set('numDVs'='10','numNulls'='0','highValue'='800','lowValue'='-1');
> explain select count (1) from t1,t2
> where t1.j=t2.i2
> group by t1.i, t1.j;
> {code}
> {code:sql}
> Reducer 2
> Reduce Operator Tree:
> Merge Join Operator
> condition map:
> Inner Join 0 to 1
> keys:
> 0 _col1 (type: int)
> 1 _col0 (type: int)
> outputColumnNames: _col0, _col1
> Statistics: Num rows: 99700 Data size: 797288 Basic stats:
> COMPLETE Column stats: COMPLETE
> Group By Operator
> aggregations: count()
> keys: _col0 (type: int), _col1 (type: int)
> mode: hash
> outputColumnNames: _col0, _col1, _col2
> Statistics: Num rows: 49850 Data size: 797448 Basic stats:
> COMPLETE Column stats: COMPLETE <==========
> Reduce Output Operator
> key expressions: _col0 (type: int), _col1 (type: int)
> sort order: ++
> Map-reduce partition columns: _col0 (type: int), _col1
> (type: int)
> Statistics: Num rows: 49850 Data size: 797448 Basic
> stats: COMPLETE Column stats: COMPLETE
> value expressions: _col2 (type: bigint)
> .....................
> {code}
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