[jira] [Commented] (LENS-752) Support flattening of columns selected through bridge-tables(many-to-many relationships)

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

    [ https://issues.apache.org/jira/browse/LENS-752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14907458#comment-14907458 ] 

Hadoop QA commented on LENS-752:
--------------------------------

Applied patch: [LENS-752.3.patch|https://issues.apache.org/jira/secure/attachment/12762302/LENS-752.3.patch] and ran command: mvn clean install. Result: Success. Build Job: https://builds.apache.org/job/PreCommit-Lens-Build/79/

> Support flattening of columns selected through bridge-tables(many-to-many relationships)
> ----------------------------------------------------------------------------------------
>
>                 Key: LENS-752
>                 URL: https://issues.apache.org/jira/browse/LENS-752
>             Project: Apache Lens
>          Issue Type: New Feature
>          Components: cube
>            Reporter: Amareshwari Sriramadasu
>            Assignee: Amareshwari Sriramadasu
>             Fix For: 2.4
>
>         Attachments: LENS-752.3.patch
>
>
> Data warehousing concepts suggests to use bridge-tables to implement many-to-many relationships between cube & dimension or between two dimensions.
> Here are few links explaining the bridge-tables
> http://www.pythian.com/blog/implementing-many-to-many-relationships-in-data-warehousing/
> http://www.kimballgroup.com/2012/02/design-tip-142-building-bridges/
> http://stackoverflow.com/questions/2785158/star-schema-fact-1n-dimension-how
> http://www.askjohnobiee.com/2013/08/how-to-bridge-tables-and-many-to-many.html
> If we look at the following schema :
> User :
> |ID|Name|Gender|
> |1|A|M|
> |2|B|M|
> |3|C|F|
> User interests :
> |UserID| Sports ID|
> |1|1|
> |1|2|
> |2|1|
> |2|2|
> |2|3|
> Sports :
> |SportsID| Description|
> |1|Football|
> |2|Cricket|
> |3|Basketball|
> User Interests is the bridge table which is capturing the many-to-many relationship between Users and Sports.
> If we have a fact as follows :
> |UserId| Revenue|
> |1|100|
> |2|50|
> If analyst is interested in analyzing with respect to user's interest, then the report would the following :
> |User Interest|Revenue|
> |Football|150|
> |Cricket|150|
> |BasketBall|50|
> Though the individual rows are correct and the overall revenue is actually 150, looking at above report makes people assume that overall revenue is 350.
> The feature ask here is to optionally flatten the selected fields, if fields involved are coming from bridge tables in join path. If flattening is enabled, the report would be the following :
> |User Interest|Revenue|
> |Football, Cricket|100|
> |Football, Cricket, BasketBall|50|



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