[OASIS Issue Tracker] (ODATA-904) Example 55: clarify groupby in combination with relationships of instance cardinality zero

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

Ralf Handl created ODATA-904:
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             Summary: Example 55: clarify groupby in combination with relationships of instance cardinality zero
                 Key: ODATA-904
                 URL: https://issues.oasis-open.org/browse/ODATA-904
             Project: OASIS Open Data Protocol (OData) TC
          Issue Type: Bug
          Components: OData Extension for Data Aggregation
    Affects Versions: V4.0_CS02
         Environment: Proposed
            Reporter: Ralf Handl
             Fix For: V4.0_CSD04


Example 55:

  GET ~/Customers?$apply=groupby((Country,Sales/Product/Name))

The example result does not contain an entry for country France. The example data contains a customer in France that does not have any sales.

The prose text before the example states expansion "in a left-outer-join fashion".

This would suggest that a result row is missing:

  { "@odata.id": null, "Country": "France", "Sales": [ { "Product": { "Name": null } } ] }

This would be consistent with both the left-outer-join statement and the URL conventions for path expressions where properties of related entities are treated as null if no entity is related:
- the left-outer join would produce a single Sales row containing only null values, including the related product and its name
- this would create a ("France",null) group during aggregation
- folding back into the original shape would create the additional entry



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