Details
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Improvement
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Status: Closed
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Major
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Resolution: Fixed
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0.14.0, 1.0.1, 1.1.1, 1.2.1, 1.3.0, 2.0.0
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Use fastest hashmap implementation of ExprNodeDesc lookups
Description
Due to the absence of ExprNodeDesc::equals() & the presence of a hashCode(), any code which computes a Set or HashMap of identical objects ends up with a skewed hashmap which degrades column lookups from O(1) to O(N) during optimizer passes.
So, several hundred references to a single column desc will be stored in a single hashbucket, but since they default to Object::equals(), they are not equal to each other.
Finalize the equals() method, so that the approach from HIVE-10215 carries over safely.
Attachments
Attachments
Issue Links
- is part of
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HIVE-11315 Compilation performance issues for large queries
- Resolved
- is related to
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HIVE-11627 Reduce the number of accesses to hashmaps in PPD
- Closed