liyang created KYLIN-3423:
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Summary: Performance improvement in FactDistinctColumnsMapper
Key: KYLIN-3423
URL: https://issues.apache.org/jira/browse/KYLIN-3423
Project: Kylin
Issue Type: Improvement
Reporter: liyang
Currently FactDistinctColumnsMapper writes every cell to mapper output. In
spite of mapper side Combiner, we could do better de-dup using available mapper
memory.
The situation becomes worse after KYLIN-3370, because not only dictionary
columns, now it is every dimension column get written as mapper output.
Suggest
* Use available mapper memory to de-dup before write to mapper output.
* For non-dictionary dimension column, only write min/max value to mapper
output.
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