[jira] [Commented] (KYLIN-2286) global snapshot table for one cube

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

    [ https://issues.apache.org/jira/browse/KYLIN-2286?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15753713#comment-15753713 ] 

Shaofeng SHI commented on KYLIN-2286:
-------------------------------------

This sounds like the scenario of "Slowly Changing Dimensions", which isn't well supported today: If user wants get history cube be updated (after changing lookup table), he need go back to refresh those history segments. 

Yu, is there any prediction for using global snapshot? I think all dimension columns in lookuptable should be "drived", right?



> global snapshot table for one cube 
> -----------------------------------
>
>                 Key: KYLIN-2286
>                 URL: https://issues.apache.org/jira/browse/KYLIN-2286
>             Project: Kylin
>          Issue Type: Improvement
>            Reporter: fengYu
>            Assignee: fengYu
>
> I current version, Kylin build a snapshot table for a segment and isolate with each other in the same cube,  even though some segments share the same snapshot table storage  .
> I some scene， we need global snapshot table for one cube, such as we has a cube with snapshot table,ID is PK，the first day, the table look like:
> id name
> 1   A
> 2   B
> 3   C
> the query 'select name, count(1) from fact join dimension group by name' get result:
> A xx
> B xx
> C xx
> the next day(segment), lookup table modified, it looks like :
> id name
> 1   A
> 2   D
> 3   E
> the same query return :
> A xx
> B xx
> C xx
> D xx
> E xx
> However B and D, C and E has the same ID, we need the newest result. so a global snapshot table shared by all segments which has always the newest values is needed.



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