Rajkumar Singh created HIVE-19192:
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Summary: HiveServer2 query compilation : query compilation time
increases sql has multiple unions
Key: HIVE-19192
URL: https://issues.apache.org/jira/browse/HIVE-19192
Project: Hive
Issue Type: Improvement
Components: Hive, HiveServer2
Affects Versions: 2.1.0, 1.2.1
Environment: Hive-1.2.1
Hive-2.1.0
Reporter: Rajkumar Singh
Attachments: query-with-100-union.q, query-with-200-union.q,
query-with-50-union.q
query compilation time suffer a lot if SQL has many unions, here is the simple
reproduce of the problem. PFA attached query with 50,100 and 200 unions(forgive
me for this bad SQL). when run explain against hiveserver2 I can see the
compilation time increase many folds.
{code}
query-with-50-union.q
1,671 rows selected (10.662 seconds)
query-with-100-union.q
3,321 rows selected (101.709 seconds)
query-with-200-union.q
6,588 rows selected (1074.487 seconds)
{code}
Running such SQL against hiveserver2 can starve other SQL to run into single
threaded compilation stage.
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