[RFC] set based apis...

[Ian Clatworthy]

Robert Collins wrote:
> I'd like to start a pattern of methods that deal with historical data.
> The pattern is to query for sets, and return iterators that are self
> describing so that the returned order can vary from the requested one.
> We should allow the order to be defined only when it really matters -
> but when we allow it we probably want to allow it all the way down.
> 
> This is to allow effective read coalescing and index scanning without
> requiring in-memory sort by the lowest layers.
> 
> Thoughts?
> 
> -Rob

Generally speaking, what you're proposing is great policy. If there is
no need to force a constraint on an API, don't do it because it
restricts implementation choices.

Ian C.