[jira] [Commented] (DRILL-5527) Support for querying slowly changing dimensions of HBase/MapR-DB tables on TIMESTAMP/TIMERANGE/VERSION

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

    [ https://issues.apache.org/jira/browse/DRILL-5527?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16017558#comment-16017558 ] 

Julian Hyde commented on DRILL-5527:
------------------------------------

I think it would be best if we did this in the relational way. In the relational model a column has only one value, and the update timestamp is a column that belongs to the row. 

So let's suppose that each time a columns value is changed, Drill makes an entire new row appear. The row the same key as the previous row, but a new timestamp or sequence number. Or perhaps the new row has a surrogate key that is unique across the whole table. 

This is how people manage SCDs in traditional kimbal data warehousing. I think it is the simplest way to expose it for Drill users. 

> Support for querying slowly changing dimensions of HBase/MapR-DB tables on TIMESTAMP/TIMERANGE/VERSION
> ------------------------------------------------------------------------------------------------------
>
>                 Key: DRILL-5527
>                 URL: https://issues.apache.org/jira/browse/DRILL-5527
>             Project: Apache Drill
>          Issue Type: New Feature
>          Components: Storage - HBase
>    Affects Versions: 1.10.0
>            Reporter: Alan Fischer e Silva
>
> HBase and MapR-DB support versioning of cell values via timestamp, but today a Drill query only returns the most recent version of a cell.
> Being able to query an HBase/MapR-DB cell on it's version, timestamp or timerange would be a major improvement to the HBase storage plugin in order to support slowly changing dimensions.



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