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Posted to issues@kylin.apache.org by "kangkaisen (JIRA)" <ji...@apache.org> on 2016/05/16 04:21:12 UTC

[jira] [Created] (KYLIN-1695) disable cardinality calculation job when loading hive table

kangkaisen created KYLIN-1695:
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             Summary: disable cardinality calculation job when loading hive table
                 Key: KYLIN-1695
                 URL: https://issues.apache.org/jira/browse/KYLIN-1695
             Project: Kylin
          Issue Type: Bug
          Components: Job Engine
    Affects Versions: v1.5.1
            Reporter: kangkaisen
            Assignee: Dong Li


When user loads/reloads hive tables from web console, kylin will submit a mr job asynchronously to calculate column cardinalities. This has four major problems:

# the calculated cardinality is stored in table metadata, but never used in cubing/querying
# table may change after loading, so the cardinality doesn't necessarily reflect the actual value
# the current `HiveColumnCardinalityJob` has many limitations, e.g., it doesn't support views
# the `HiveColumnCardinalityJob` may use lots of resources when computing cardinality of partitioned table

Due to these problems, we should disable it by default and (maybe) remove it in future releases.



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