[OASIS Issue Tracker] (ODATA-1349) Calculate Custom Aggregates from Aggregated Instances

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

Gerald Krause created ODATA-1349:
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             Summary: Calculate Custom Aggregates from Aggregated Instances
                 Key: ODATA-1349
                 URL: https://issues.oasis-open.org/browse/ODATA-1349
             Project: OASIS Open Data Protocol (OData) TC
          Issue Type: New Feature
          Components: Data Aggregation
    Affects Versions: V4.0_CS02
         Environment: [Proposed]
            Reporter: Gerald Krause
             Fix For: V4.0_CSD04


A CustomAggregate annotation defines a dynamic property that can be used in the aggregate transformation. The current document states in [6.2.3 Custom Aggregates|http://docs.oasis-open.org/odata/odata-data-aggregation-ext/v4.0/cs02/odata-data-aggregation-ext-v4.0-cs02.html#_Toc435016600], second paragraph: âWhen applied to a structured type, the annotation specifies custom aggregates that are available for collections of _instances of that structured type_.â

This also means that a custom aggregate cannot be applied to an intermediate, already aggregated result produced by $apply transformations. Such a result consists of aggregated instances that are based on the structure of the instances from which they have been calculated ([4ÂÂÂÂÂÂÂ Representation of Aggregated Instances|http://docs.oasis-open.org/odata/odata-data-aggregation-ext/v4.0/cs02/odata-data-aggregation-ext-v4.0-cs02.html#_Toc435016593]) and some properties from the originating type have been aggregated away.

This limits the applicability of custom aggregates and prevents requests for use cases like this example: For a custom aggregate âAmountâ, determine the total amount for countries with a sales amount greater than X:

{{GET ~/Sales?$apply=groupby((Country),Amount)/filter(Amount gt X)/aggregate(Amount)}}

This can be a valid request under the assumption that {{Amount}} can be calculated for a set of aggregated instances each having a value for the {{Amount}} property.



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