[OASIS Issue Tracker] (ODATA-827) introduce $compute query option

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

    [ https://issues.oasis-open.org/browse/ODATA-827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=61351#comment-61351 ] 

Ralf Handl commented on ODATA-827:
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Rolling this into $select was the original proposal in ODATA-9. Sticking to the syntax established with aggregate() and compute() your examples would be

* ~/lineItems?$select=*,price mul quantity as total 
* ~/orders?$expand=lineItems(select=*,price mul quantity as total) 
* ~/lineItems?$select=*,price mul quantity as total&$orderby=total desc

The last example shows an interesting point: $select is currently defined to be logically evaluated after $orderby, i.e. one can order by properties that are not returned. Instead of introducing two places for requesting computed properties I'd rather except computed fields from this rule and define them to be logically computed as late as possible.

> introduce $compute query option
> -------------------------------
>
>                 Key: ODATA-827
>                 URL: https://issues.oasis-open.org/browse/ODATA-827
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Improvement
>          Components: OData Protocol, OData URL Conventions
>    Affects Versions: V4.0_WD01
>         Environment: New Query Capabilities
>            Reporter: Andrew Eisenberg
>              Labels: GoodIdea, Usability
>             Fix For: V4.01_WD01
>
>
> OData could be extended to allow derived computed values to be returned along with the properties of an entity.
> This could be expressed as:
> http://odata.netflix.com/v2/Catalog/Titles?$compute=substring(ShortSynopsis,20) as Summary&$select=Name,Summary
> In ODATA-9 we added support for an equivalent compute transformation in our Data Aggregation Extensions. 



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