[jira] [Commented] (KYLIN-1855) Should exclude those joins in whose related lookup tables no dimensions are used in cube

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

    [ https://issues.apache.org/jira/browse/KYLIN-1855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15635583#comment-15635583 ] 

liyang commented on KYLIN-1855:
-------------------------------

I'm afraid we have to re-think this issue, since we find that being too smart cause other (more serious) problems.

We encounter a case that one model have multiple cubes, but the count from different cubes gives different values. After troubleshooting, the cause is because the cubes have different lookup joins. The previous patch made the flat table is depend on cube rather than model.

However, I do think cube is an index of data, and it's model that defines data. So given the same model (thus same data), all the cube should receive the same input.

Any comment?

> Should exclude those joins in whose related lookup tables no dimensions are used in cube
> ----------------------------------------------------------------------------------------
>
>                 Key: KYLIN-1855
>                 URL: https://issues.apache.org/jira/browse/KYLIN-1855
>             Project: Kylin
>          Issue Type: Improvement
>            Reporter: Zhong Yanghong
>            Assignee: Zhong Yanghong
>             Fix For: v1.5.4
>
>         Attachments: exclude_unused_joins.patch
>
>
> A cube is based on a model in which a star schema is defined. In some cases, the cube utilizes only a few lookup tables rather than all. In this case, when creating the sql for the flat table, those lookup tables should not be included. Otherwise, it will confuse users when query. If users do query according to the definition of the flat table, error of no realization will occur due to lack of the related join.



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