jacobat / map_test

Showing a Rails issue with WeakMap

Run this in a Rails console:

u = User.find_or_initialize_by(email: "[e-mail]")
10_000.times { u.update(email: "[e-mail]") }

Observe how the time to perform the update is gradually becoming longer and longer.

One run started at:

  0.000012   0.000005   0.000017 (  0.000010)

and after running for a bit has reached:

  0.001281   0.000014   0.001295 (  0.001326)

Now let's try wrapping the updates in transactions:

u = User.find_or_initialize_by(email: "[e-mail]")
10.times do
  User.transaction do
    1000.times { u.update(email: "[e-mail]") }
  end  
end

Performance is now much more stable. All reported measurements are around:

  0.000007   0.000001   0.000008 (  0.000008)

The output is generated by the monkey patch in config/initializers/transaction_patch.rb.