I'm facing a severe performance degradation of performance in 9.0.5

[cperezabo]

The same code (a simple loop that executes a few hundred save!) that runs in 2s with 9.0.4 takes more than 30s with 9.0.5.
I just switch versions in bundle, re run and performance goes to hell!
I had also updated Ruby to 3.4.1 and thought that could have been that but, after downgrading Ruby to the previous version, the issue was still there.

Update 1:
Ok, I started testing my code with every mongoid commit after the v9.0.4 tag and the issue was introduced in 86f49a5

Update 2:
I've installed 9.0.5 again, edited the gem by reverting just the change introduced in 86f49a5 and everything performs fine as always. So there it is the problem!

[comandeo-mongo]

Hi @cperezabo , thank you for raising the issue! We are sorry that you are experiencing problems with Mongoid, we'll take a look into it. I created JIRA ticket to track the work - https://jira.mongodb.org/browse/MONGOID-5848

[comandeo-mongo]

Hi @cperezabo , can you please provide us with a snippet of code that reproduces the issue? I tried a naive variation, and I do not see a performance degradation in the benchmarks:

class Foo
  include Mongoid::Document
  field :name, type: String
  has_many :bars
  # same with embeds_many :bars
end

class Bar
  include Mongoid::Document
  field :name, type: String
  belongs_to :foo
  # same with embedded_in :foo
end

Benchmark.bm do |x|
  x.report('save!') do
    1000.times do |i|
      foo = Foo.new(name: "Foo #{i}")
      foo.bars = 100.times.map { |j| Bar.new(name: "Bar #{j}") }
      foo.save!
    end
  end
end

Thank you for your cooperation!

[cperezabo]

Hi, I copied my full class hierarchy to a single file, removed everything but the Mongoid related stuff and I was able to reproduce the issue.

With 9.0.4

With 9.0.5

The code:

require "mongoid"

Mongoid.configure do |config|
  config.clients.default = { uri: ENV.fetch("MONGODB_URL") }
end

class Ubicacion
  include Mongoid::Document

  store_in collection: "ubicaciones"

  field :descripcion
end

class Almacenamiento < Ubicacion
  field :capacidad, type: Integer
end

class Contenedor < Ubicacion
  # no Mongoid stuff here, just domain-specific behavior
end

class Celda < Almacenamiento
  field :x, type: Integer
  field :y, type: Integer

  belongs_to :rack, class_name: "Rack"
end

class Rack < Contenedor
  has_many :celdas, class_name: Celda, inverse_of: :rack
end

Benchmark.bm do |r|
  r.report("save!") do
    rack = Rack.new(descripcion: "Rack")
    rack.save!
    (0...15).each do |x|
      (0...15).each do |y|
        celda = Celda.new(x:, y:, rack:)
        rack.celdas << celda
        celda.save!
      end
    end
  end
end

[cperezabo]

Do you need me to post the answer in the Jira ticket instead?

[jamis]

You're fine to post it here, @cperezabo. Thanks for the update! Sorry to be slow in acknowledging it, we've had some sickness on our team this week and have been limping along. We'll have our triage meeting on Monday and will discuss how to proceed with this at that point.

[comandeo-mongo]

Hi @cperezabo , I posted an update on this issue in JIRA - https://jira.mongodb.org/browse/MONGOID-5848. I am not sure if you watch the ticket, so I am letting you know here as well.