Improve caching results.

[David Picó]

The collector needs to be clever about caching results

[Daniel Widerin (saily)]

i've created a new branch on repository and added my first caching implementation for collector-creation in newsletter send method. http://dev.plone.org/collective/changeset/71082

feedback welcome...

[Daniel Nouri (daniel.nouri)]

Thanks, the implementation looks almost perfect. The last problem I'm seeing with it is that it's expecting the type of metadata['cue'] to be of type datetime. Strictly speaking, only the collector knows what its type is though. So I'd suggest we move the caching to collective.dancing.collector.Collector.get_items. Maybe it'll be a bit harder to cache on the request since it's not a view. But in the end, it'll make for a more robust implementation that'll also support collectors that don't use datetime as their metadata['cue'].