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  1. Pentaho BA Platform
  2. BISERVER-3522

Slowly changing dimension (type 2) with parent child hierarchy

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    Details

    • Type: New Feature
    • Status: Closed
    • Severity: None
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: Backlog
    • Component/s: None
    • Labels:
      None
    • Notice:
      When an issue is open, the "Fix Version/s" field conveys a target, not necessarily a commitment. When an issue is closed, the "Fix Version/s" field conveys the version that the issue was fixed in.

      Description

      Question from customer:

      Will Mondrian be able to handle slowly changing dimension (type 2) with parent child hierarchy? Whenever the hierarchy changes we update the closure table to contain only the most recent hierarchy which makes me wonder how it is handling the changes to hierarchy.

      From Julian:

      It sounds like the customer has analyzed it right, and they would see a skew.
      You could try building the closure table in terms of the surrogate keys rather than user keys. (E.g. employee-version-id rather than employee-id in the standard employee parent-child hierarchy.) If they get that working, it would give the right numbers.
      Is the structure of the hierarchy slowly changing? (E.g. can an employee work for different bosses over time, in addition to non-structural changes like employee's age changing.) That would make the problem more complicated. A closure table based on surrogate keys might solve that problem too.
      Also, we only really support single-level parent-child hierarchies (i.e. all members belong to the same level) and sometimes people want to model the 'versions' as an additional level. You wouldn't be able to do that.
      We would also like to log a feature request whether we can meet or otherwise your requirements currently. Could you please describe your specific requirements based on the info given so that I may log request?

      From Customer:

      was able to build the closure table with the surrogate key like Julian said and it appears to be working fine.
      I need to know the reason because leadership is not going to like it if I propose to change the data model without any concrete reasoning.

      Julian requested the Jira.

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            Assignee:
            jhyde Julian Hyde (Inactive)
            Reporter:
            anthonycarter Anthony Carter (Inactive)
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              Dates

              Created:
              Updated:
              Resolved: