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