Rajesh Balamohan created HIVE-22850:
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Summary: Optimise lock acquisition in TxnHandler
Key: HIVE-22850
URL: https://issues.apache.org/jira/browse/HIVE-22850
Project: Hive
Issue Type: Improvement
Components: Hive
Reporter: Rajesh Balamohan
With concurrent queries, time taken for lock acquisition increases
substantially. As part of lock acquisition in the query,
{{TxnHandler::checkLock}} gets invoked. This involves getting a mutex and
compare the locks being requested for, with that of existing locks in
{{HIVE_LOCKS}} table.
With concurrent queries, time taken to do this check increase and this
significantly increases the time taken for getting mutex for other threads. In
a synthetic workload, it was in the order of 10+ seconds. This codepath can be
optimized when all lock requests are SHARED_READ.
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