Remus Rusanu created HIVE-16790:
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Summary: HiveCostModel.JoinAlgorithm and derivatives abuse
RelMetadataQuery.instance
Key: HIVE-16790
URL: https://issues.apache.org/jira/browse/HIVE-16790
Project: Hive
Issue Type: Bug
Components: Query Planning
Reporter: Remus Rusanu
Assignee: Remus Rusanu
Calling {{RelMetadataQuery.instance()}} has serious performance implication, as
it invalidates the memoization cache used in Calcite, see HIVE-16757
{{HiveCostModel.JoinAlgorithm}} and the derivate classes abuse this calls,
sometimes multiple times per function. All methods in JoinAlgortihm that need a
RelMetadataQuery should accept it as argument, not build one instance.
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