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https://issues.apache.org/jira/browse/HIVE-21028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16720681#comment-16720681
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Hive QA commented on HIVE-21028:
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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}  7m 
52s{color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  0m 
23s{color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 
 6s{color} | {color:green} master passed {color} |
| {color:blue}0{color} | {color:blue} findbugs {color} | {color:blue}  1m  
1s{color} | {color:blue} standalone-metastore/metastore-server in master has 
188 extant Findbugs warnings. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
19s{color} | {color:green} master passed {color} |
|| || || || {color:brown} Patch Compile Tests {color} ||
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  0m 
27s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  0m 
23s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  0m 
23s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 
 7s{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}  1m  
7s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
18s{color} | {color:green} the patch passed {color} |
|| || || || {color:brown} Other Tests {color} ||
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  0m 
12s{color} | {color:green} The patch does not generate ASF License warnings. 
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| {color:black}{color} | {color:black} {color} | {color:black} 12m 41s{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-15305/dev-support/hive-personality.sh
 |
| git revision | master / b5b6371 |
| Default Java | 1.8.0_111 |
| findbugs | v3.0.0 |
| modules | C: standalone-metastore/metastore-server U: 
standalone-metastore/metastore-server |
| Console output | 
http://104.198.109.242/logs//PreCommit-HIVE-Build-15305/yetus.txt |
| Powered by | Apache Yetus    http://yetus.apache.org |


This message was automatically generated.



> get_table_meta should use a fetch plan to avoid race conditions ending up in 
> NucleusObjectNotFoundException
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-21028
>                 URL: https://issues.apache.org/jira/browse/HIVE-21028
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Karthik Manamcheri
>            Assignee: Karthik Manamcheri
>            Priority: Major
>         Attachments: HIVE-21028.1.patch, HIVE-21028.2.patch, 
> HIVE-21028.3.patch, HIVE-21028.4.patch, HIVE-21028.5.patch
>
>
> The {{getTableMeta}} call retrieves the tables, loops through the tables and 
> during this loop it retrieves the database object to get the containing 
> database name. DataNuclues does a lazy retrieval and so, when the first call 
> to get all the tables is done, it does not retrieve the database objects.
> When this query is executed
> {code}query = pm.newQuery(MTable.class, filterBuilder.toString());
> {code}
> it loads all the tables, and when you do
> {code}
> table.getDatabase().getName()
> {code}
> it then goes and retrieves the database object.
> *However*, there could be another thread which actually has deleted the 
> database!! If this happens, we end up with exceptions such as
> {code}
> 2018-12-04 22:25:06,525 INFO  DataNucleus.Datastore.Retrieve: 
> [pool-7-thread-191]: Object with id 
> "6930391[OID]org.apache.hadoop.hive.metastore.model.MTable" not found !
> 2018-12-04 22:25:06,527 WARN  DataNucleus.Persistence: [pool-7-thread-191]: 
> Exception thrown by StateManager.isLoaded
> No such database row
> org.datanucleus.exceptions.NucleusObjectNotFoundException: No such database 
> row
> {code}
> We see this happen especially with calls which retrieve all the tables in all 
> the databases (basically a call to get_table_meta with dbNames="\*" and 
> tableNames="\*").
> To avoid this, we can define a custom fetch plan and activate it only for the 
> get_table_meta query. This fetch plan would fetch the database object along 
> with the MTable object.
> We would first create a fetch plan on the pmf
> {code}
> pmf.getFetchGroup(MTable.class, 
> "mtable_db_fetch_group").addMember("database");
> {code}
> Then we use it just before calling the query
> {code}
> pm.getFetchPlan().addGroup("mtable_db_fetch_group");
> query = pm.newQuery(MTable.class, filterBuilder.toString());
> Collection<MTable> tables = (Collection<MTable>) query.executeWithArray(...);
> ...
> {code}
> Before the API call ends, we can remove the fetch plan by
> {code}
> pm.getFetchPlan().removeGroup("mtable_db_fetch_group");
> {code}



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