RE: [odata-comment] Function invocation in $select

Hi Hans,

We’ve considered this early on, see ODATA-9, and decided to defer it to a later version of the specification.

In the meantime we’ve used a similar syntax in the OData Extension for Data Aggregation for aggregate expressions, and in fact you could simulate the extended $select syntax sketched in ODATA-9 with the $apply query option:

GET Something?$apply=groupby((<list of key properties>),aggregate(<_expression_ 1> with max as alias_1,…,<_expression_ n> with max as alias_n))

So extending the $select syntax as sketched in ODATA-9 seems quite natural, but at this point in time we can’t add it to the OASIS standard specification without increasing the protocol version number.

Thanks!
--Ralf

From: odata-comment@lists.oasis-open.org [mailto:odata-comment@lists.oasis-open.org] On Behalf Of Hans van Bakel
Sent: Donnerstag, 19. März 2015 20:16
To: odata-comment@lists.oasis-open.org
Subject: [odata-comment] Function invocation in $select

Hi,

I was wondering if there's a specific design decision/reason for not supporting the invocation of functions/actions within the $select parameter while the $orderby and $filter parameters do support invoking an instance function.

What I am trying to achieve is to get the result of the invocation of a function as a value in my resultset. So the function gets evaluated for every item in my resultset (just as would happen if I add it to $fitler or $orderby). The name of the property would be the function name for example.

Right now I only see the option (in the ABNF) to request the path to the function, there's no way to invoke it. But that would require me to make N+1 queries in order to get the result of the function to my client.

Thanks,

Hans

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