How to use Partitions?

I notice when defining a projection, there is a field above the “state” output that lets you specify a “partition”.

I assume this is related to projections having a “partitionBy” concept.
Is there any example of this working I can look at?



In my example, I have a streams related to products (1 stream per product that has various events)

If you create a projection like this:

            $init: function() {
                return {}
        $any: function(s, e) {
            //TODO: build your state up

And then once it’s caught up, simply paste one of the stream name into that textbox, you will see the partition of that stream (maybe initialy, just do s.count++ to verify it’s really working)

Hope that helps.