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Posted to issues-all@impala.apache.org by "Tim Armstrong (JIRA)" <ji...@apache.org> on 2018/06/19 17:38:00 UTC
[jira] [Resolved] (IMPALA-3948) Impala JDBC driver blocks
concurrent queries when UseNativeQuery=0
[ https://issues.apache.org/jira/browse/IMPALA-3948?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tim Armstrong resolved IMPALA-3948.
-----------------------------------
Resolution: Invalid
The driver isn't part of Apache Impala
> Impala JDBC driver blocks concurrent queries when UseNativeQuery=0
> ------------------------------------------------------------------
>
> Key: IMPALA-3948
> URL: https://issues.apache.org/jira/browse/IMPALA-3948
> Project: IMPALA
> Issue Type: Bug
> Components: Clients
> Affects Versions: Impala 2.5.0
> Reporter: Julian Eberius
> Assignee: Syed A. Hashmi
> Priority: Minor
>
> When using the Impala JDBC driver verison 2.5.32 and a standard connection pool in a Java application to run concurrent queries, I discovered that all application threads executing Impala queries where blocked except for one. All others were hanging in HiveJDBCQueryExecutorWithLimitZeroPreparedStatementMetadata#execute(ExecutionContexts, IWarningListener). I further investigated the decompiled code of this method and found a synchronized() statement, which locks on a global singleton of type IQueryTranslator and encloses an executeQuery() call. This effectively makes the whole driver single-threaded, which should not be the case for standards-conforming JDBC drivers as far as I know.
> When using the parameter UseNativeQuery=1, the driver uses the class HiveJDBCNativeQueryExecutor instead of HiveJDBCQueryExecutorWithLimitZeroPreparedStatementMetadata, which does not have this synchronized statement. In this case, all queries were submitted to Impala in parallel, which is the expected behavior.
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