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Posted to dev@kylin.apache.org by "liyang (JIRA)" <ji...@apache.org> on 2018/06/21 09:13:00 UTC

[jira] [Created] (KYLIN-3423) Performance improvement in FactDistinctColumnsMapper

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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