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https://issues.apache.org/jira/browse/HIVE-21028?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Karthik Manamcheri updated HIVE-21028:
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Summary: get_table_meta should use a fetch plan to avoid race conditions
ending up in JDOObjectNotFoundException (was: get_table_meta should use a
fetch plan)
> get_table_meta should use a fetch plan to avoid race conditions ending up in
> JDOObjectNotFoundException
> -------------------------------------------------------------------------------------------------------
>
> 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
>
> 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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