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https://issues.apache.org/jira/browse/HIVE-20332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16572240#comment-16572240
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Hive QA commented on HIVE-20332:
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| (x) *{color:red}-1 overall{color}* |
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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:blue}0{color} | {color:blue} mvndep {color} | {color:blue}  0m 
37s{color} | {color:blue} Maven dependency ordering for branch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  7m 
26s{color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m 
14s{color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 
53s{color} | {color:green} master passed {color} |
| {color:blue}0{color} | {color:blue} findbugs {color} | {color:blue}  0m 
29s{color} | {color:blue} common in master has 64 extant Findbugs warnings. 
{color} |
| {color:blue}0{color} | {color:blue} findbugs {color} | {color:blue}  3m 
44s{color} | {color:blue} ql in master has 2305 extant Findbugs warnings. 
{color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  1m  
7s{color} | {color:green} master passed {color} |
|| || || || {color:brown} Patch Compile Tests {color} ||
| {color:blue}0{color} | {color:blue} mvndep {color} | {color:blue}  0m  
8s{color} | {color:blue} Maven dependency ordering for patch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  1m 
36s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m 
15s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  1m 
15s{color} | {color:green} the patch passed {color} |
| {color:red}-1{color} | {color:red} checkstyle {color} | {color:red}  0m 
39s{color} | {color:red} ql: The patch generated 4 new + 213 unchanged - 1 
fixed = 217 total (was 214) {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 
35s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  1m 
10s{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. 
{color} |
| {color:black}{color} | {color:black} {color} | {color:black} 26m  4s{color} | 
{color:black} {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-13086/dev-support/hive-personality.sh
 |
| git revision | master / c0f63bf |
| Default Java | 1.8.0_111 |
| findbugs | v3.0.0 |
| checkstyle | 
http://104.198.109.242/logs//PreCommit-HIVE-Build-13086/yetus/diff-checkstyle-ql.txt
 |
| modules | C: common ql U: . |
| Console output | 
http://104.198.109.242/logs//PreCommit-HIVE-Build-13086/yetus.txt |
| Powered by | Apache Yetus    http://yetus.apache.org |


This message was automatically generated.



> Materialized views: Introduce heuristic on selectivity over ROW__ID to favour 
> incremental rebuild
> -------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-20332
>                 URL: https://issues.apache.org/jira/browse/HIVE-20332
>             Project: Hive
>          Issue Type: Improvement
>          Components: Materialized views
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>            Priority: Major
>         Attachments: HIVE-20332.patch
>
>
> Currently, we do not expose stats over {{ROW\_\_ID.writeId}} to the optimizer 
> (this should be fixed by HIVE-20313). Even if we did, we always assume 
> uniform distribution of the column values, which can easily lead to 
> overestimations on the number of rows read when we filter on 
> {{ROW\_\_ID.writeId}} for materialized views (think about a large transaction 
> for MV creation and then small ones for incremental maintenance). This 
> overestimation can lead to incremental view maintenance not being triggered 
> as cost of the incremental plan is overestimated (we think we will read more 
> rows than we actually do). This could be fixed by introducing histograms that 
> reflect better the column values distribution.
> Till both fixes are implemented, we will use a config variable that will set 
> the selectivity for filter condition on {{ROW\_\_ID}} during the cost 
> calculation. Setting that variable to a low value will favour incremental 
> rebuild over full rebuild.



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