What this is about?

You have probably heard of N+1 queries problem. In the rails community, there are a bullet and rspec-sqlimit gems that help to detect this kind of queries. sequel_query_limit is a Sequel extension that pursuits the very much similar goal as rspec-sqlimit does. Maybe a little more :)

Usage

With RSpec

module SqlSpecHelper
  def self.included(base)
    base.before(:each) { QueryLimit::Listener::Global.watch }
    base.after(:each)  { QueryLimit::Listener::Global.analyze(np1: true, reset: true) }
    base.after(:all)   { QueryLimit::Listener::Global.die }
  end
end

RSpec.configure do |config|
  config.include SqlSpecHelper, watch: :np1
end

RSpec.describe 'analyzer', watch: :np1 do
  it 'analyzes queries that has been run' do
    collection = Models::Company.limit(10).all
    App::Companies::Serializer.for_collection.new(collection).to_hash
    expect(true).to eq true
  end
end

Using this technique you can check individual examples for N+1 quries withouth wrapping everything into DB.with_query_limit block.

#with_query_limit

Maybe useful for ad-hoc testing via console. This also can be used in tests.

DB.with_query_limit(/SELECT/, max: 3) do
  collection = Models::Company.limit(10).all
  App::Companies::Serializer.for_collection.new(collection).to_hash
end

This will return result of your query if it's not exceeding specified max limit. Otherwise, it will raise an exception with captured sql queries.

TODO

• Add configuration option for what to do when query exceeds a limit (raise exception or run a callback)
• Add configuration option for what to do when N+1 problem found
• Add RSpec matchers
• Add option to limit by query execution time
• Add ability to pass custom sql backrace formatter
• Add ability to analyze on the fly

Contributing

Bug reports and pull requests are welcome!

License

The gem is available as open source under the terms of the MIT License.