mongodb/mongo-ruby-driver — pull request #124 by ebroder (2012-10-11 08:14:04+00:00)
Title: Only let the right mapreduce queries go to secondaries

Specifically, they should have an out parameter, the value of that out
parameter should be a hash, and the first key of that hash should be
the string or symbol inline.

Right now, secondary_ok? will return true for mapreduces if :out is not the string 'inline'.