[jira] [Commented] (KYLIN-1695) Skip cardinality calculation job when loading hive table

["Shaofeng SHI (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KYLIN-1695?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15297954#comment-15297954 ] 

Shaofeng SHI commented on KYLIN-1695:
-------------------------------------

only one comment: the checkbox lable should better be a verb, while "cardinality calculation job when loading hive table" is a noun; suggest to change it to verb like "Calculate column cardinality"; Others all looks good.

> Skip 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
>         Attachments: KYLIN-1695.patch
>
>
> 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.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)