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From "Pierre Smits (Jira)" <j...@apache.org>
Subject [jira] [Commented] (OFBIZ-10953) have CurrencyDimension have a dimensionId that is based on the natural key
Date Thu, 06 Feb 2020 12:07:00 GMT

    [ https://issues.apache.org/jira/browse/OFBIZ-10953?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17031527#comment-17031527
] 

Pierre Smits commented on OFBIZ-10953:
--------------------------------------

Currency definitions are not defined by the project, but rather by the ISO (see 1). And based
on publicly available information(this may take some time to find) the meaning of a currency
code does not change over time. As you can see in the referred webpage there have been several
updates to the currency of Zimbabwe (formerly known as Rodesia), where each new currency got
a new code while the name stayed the same. 

We can therefore safely assume/expect that over the lifespan of a country-currency relationship
the currency stays unique. We thus don't need to worry about multiple records (both in the
transaction database in the Uom table) as in the dwh in the currency dimensionTable) with
duplicate natural keys. As a fact: this is not possible because the natural key can not exist
more than once in the source table (UoM).

In DWH and BI circles it is very common to use the natural key in dimension and fact table
for currencies (as opposed to the business-own generated sequencedId for other transaction
tables), as it reduces the need to have additional effort to set up - in star schemas and
fact tables  - the relation between the (sequenced) dimensionId and what the common meaning
is (the natural key or currency code).

Even with regards to the adopted load/update strategies (type 1, type 2, etc) the DWH toolkit
book  does not dictate that values in the dimensionId field of dimension tables must be of
the sequence type.

 

 

[1] https://en.wikipedia.org/wiki/ISO_4217

> have CurrencyDimension have a dimensionId that is based on the natural key
> --------------------------------------------------------------------------
>
>                 Key: OFBIZ-10953
>                 URL: https://issues.apache.org/jira/browse/OFBIZ-10953
>             Project: OFBiz
>          Issue Type: Improvement
>          Components: bi
>    Affects Versions: Trunk, Release Branch 17.12, Release Branch 18.12
>            Reporter: Pierre Smits
>            Assignee: Pierre Smits
>            Priority: Major
>              Labels: CurrencyDimension, birt, currency, dimension, dwh
>         Attachments: OFBIZ-10953-BI.patch
>
>
> Currently the record sequencer (delegator.getNextSeqId) is used to determine the dimensionId
for the CurrencyDimension. This is unnecessary as the uomId from the UOM table can be used
for currency.
> It also makes it easier to set the foreign-key in fact tables by generating it based
on the date provided, than by retrieving the dimensionId based on a retrieval through the
getDimensionIdFromNaturalKey service.



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