gistfile1.rb

10.times do
  r = Restaurant.find(:all, :include => [:cuisines], :conditions => ['id IN (?)', ids])
  r.map(&:cuisines).flatten.map(&:id)
end

 # benchmarked 10 times
    user     system      total        real
5.540000   0.010000   5.550000 (  5.553716)
5.560000   0.000000   5.560000 (  5.566566)
5.670000   0.010000   5.680000 (  5.687871)
5.670000   0.000000   5.670000 (  5.674870)
5.580000   0.000000   5.580000 (  5.581576)
5.670000   0.000000   5.670000 (  5.678692)
5.570000   0.000000   5.570000 (  5.578353)
5.630000   0.000000   5.630000 (  5.629657)
5.740000   0.000000   5.740000 (  5.745029)
5.560000   0.000000   5.560000 (  5.568952)

# memory diff from baseline IRB for each run [1]
8896, 14608, 14800, 14932, 15024, 15152, 15248, 15300, 15300, 15300