How to get execution time in rails console?

I want compare time of execution Post.all and SELECT * FROM posts (or some other statements) How can i get execution time of Post.all ?

You can use the built-in Benchmark module:

timing = Benchmark.measure { Post.all }

The various attributes of the object returned (Benchmark::Tms) are provided here – note that they are all in seconds:

• cstime: System CPU time of children
• cutime: User CPU time of children
• label: Label
• real: Elapsed real time
• stime: System CPU time
• total: Total time, that is utime + stime + cutime + cstime
• utime: User CPU time

If you want to compare multiple measurements, you can use Benchmark.bm or Benchmark.bmbm:

Benchmark.bm do |x|
  x.report("Post.all") { Post.all }
  x.report("Measurement.all") { Measurement.all }
end

This will report the time taken for each run, so you can compare them.