Discussion on groupBy

[Orvid King via Digitalmars-d]

On Saturday, 10 January 2015 at 20:19:14 UTC, Andrei
Alexandrescu wrote:
> groupBy is an important primitive for relational algebra 
> queries on data. Soon to follow are operators such as 
> aggregate() which is a sort of reduce() but operating on ranges 
> of ranges. With those in tow, a query such as
>
> SELECT COUNT(*), SUM(x) FROM data GROUP BY userid
>
> can be expressed as:
>
> data
>  .groupBy!((a, b) => a.userid == b.userid)
>  .aggregate(count, (a, b) => a.x + b.x);
>
> We're working the kinks out groupBy now. Those interested 
> please follow at https://issues.dlang.org/show_bug.cgi?id=13936.

It would be interesting if we could make it possible to do a 
translation between D and SQL, similar to how LINQ is implemented 
internally, but preferably have it done at compile-time rather 
than at runtime.