RavenDB Map/Reduce optimizations

so i was diagnosing a customer problem, which required me to write the following:

this is working on a data set of about half a million records.

i took a peek at the stats and i saw this:

you can ignore everything before 03:23, this is the previous index run. i reset it to make sure that i have a clean test.

what you can see is that we start out with a mapping & reducing values. and you can see that initially this is quite expensive. but very quickly we recognize that we are reducing a single value, and we switch strategies to a more efficient method, and we suddenly have very little cost involved in here. in fact, you can see that the entire process took about 3 minutes from start to finish, and very quickly we got to the point where are bottle neck was actually the maps pushing data our way.

that is pretty cool.