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Posted to dev@hive.apache.org by "Gopal V (JIRA)" <ji...@apache.org> on 2014/05/29 22:57:01 UTC
[jira] [Created] (HIVE-7144) GC pressure during ORC
StringDictionary writes
Gopal V created HIVE-7144:
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Summary: GC pressure during ORC StringDictionary writes
Key: HIVE-7144
URL: https://issues.apache.org/jira/browse/HIVE-7144
Project: Hive
Issue Type: Bug
Components: File Formats
Affects Versions: 0.14.0
Environment: ORC Table ~ 12 string columns
Reporter: Gopal V
Assignee: Gopal V
Attachments: orc-string-write.png
When ORC string dictionary writes data out, it suffers from bad GC performance due to a few allocations in-loop.
!orc-string-write.png!
The conversions are as follows
StringTreeWriter::getStringValue() causes 2 conversions
LazyString -> Text (LazyString::getWritableObject)
Text -> String (LazyStringObjectInspector::getPrimitiveJavaObject)
Then StringRedBlackTree::add() does one conversion
String -> Text
This causes some GC pressure with un-necessary String and byte[] array allocations.
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