Namit Jain created HIVE-3552:
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Summary: performant manner for performing cubes and rollups in
case of less aggretation
Key: HIVE-3552
URL: https://issues.apache.org/jira/browse/HIVE-3552
Project: Hive
Issue Type: New Feature
Components: Query Processor
Reporter: Namit Jain
Assignee: Namit Jain
This is a follow up for HIVE-3433.
Had a offline discussion with Sambavi - she pointed out a scenario where the
implementation in HIVE-3433 will not scale. Assume that the user is performing
a cube on many columns, say '8' columns. So, each row would generate 256 rows
for the hash table, which may kill the current group by implementation.
A better implementation would be to add an additional stage - in the first
stage perform the group by assuming there was no cube. Ad another stage, where
you would perform the cube. The assumption is that the group by would have
decreased the output data significantly.
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