[OASIS Issue Tracker] (ODATA-1163) A Case for Common Expressions

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

Gerald Krause created ODATA-1163:
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             Summary: A Case for Common Expressions
                 Key: ODATA-1163
                 URL: https://issues.oasis-open.org/browse/ODATA-1163
             Project: OASIS Open Data Protocol (OData) TC
          Issue Type: New Feature
          Components: Protocol, URL Conventions
    Affects Versions: V4.01_CS01
            Reporter: Gerald Krause
             Fix For: V4.02_WD01


Support of case expressions as known from the SQL standard would add to the ad hoc capabilities and support use cases that require such an IF-THEN-ELSE logic.

Imagine case( condition_1, value_1, ..., condition_N, value_N [, else_value] ) would be available as canonical function for common expressions; an omitted else defaults to null. Here are some examples that could be addressed with it:

1. Core OData: Ad-hoc calculations with logic on the current property values:
Example: Signum(x)

GET ~/XValues?$compute=case(X > 0, 1,X < 0, -1, 0) as SignumX&$select=X,SignumX

2. Data Aggregation extension: Restricting aggregation to those values that occur in combination with certain groupable property values:
Example: Comparing company revenues for years 2000 and 2017

GET ~/Sales?$apply=groupby((Company), aggregate(case(Time/Year eq 2000, Revenue) with sum as TotalRevenue2000, case(Time/Year eq 2017, Revenue) with sum as TotalRevenue2017))

3. Data Aggregation extension: Defining dynamic groupable properties
Example: From a collection of incidents with fine-grained state model (e.g., new, assigned, resolved, verified, reopened, closed) retrieve the aggregated count of open and closed incidents:

GET ~/Incidents?$apply=compute(case(Status eq ‘Closed’, ‘Closed’, ‘Open’) as ProcessingStatus)/groupby((ProcessingStatus), aggregate($count as IncidentCount))




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