Query Diet 
Query Diet counts the number of database queries for the last request and subtly displays it in the upper right corner of your screen. The display turns red if too many queries are run, or if they take too long. This is useful to prevent N + 1 queries from creeping into your code.
This is Query Diet being happy about 3 requests taking 66ms:
This is Query Diet being angry about 103 requests taking 164ms:
Installation
Add it to your Gemfile with
gem 'query_diet', group: :developmentNow add the widget to your application layout, like
# app/views/layout/application.html.erb
# ...
<body>
<%= query_diet_widget if Rails.env.development? %>
<%= yield %>
</body>We recommend you only use the gem with the development environment.
Changing warning thresholds
You can define when the counter turns into a red warning. The default threshold is 8 queries and 5000 miliseconds.
To change the default, simply pass them to the query_diet_widget helper:
<%= query_diet_widget(:bad_count => 4, :bad_time => 2000) %>Content Security Policy
You can pass whether to use a nonce for style and script tags.
Note that the key must be a symbol like in the example below, otherwise it defaults to false.
<%= query_diet_widget(:nonce => true) if Rails.env.development? %>In your content security policy initializer of the project you should set the nonce to those directives:
Rails.application.config.content_security_policy_nonce_directives = %w[script-src style-src]When you do not want to use a nonce, but use a style tag, for example, you could use unsafe_inline:
Rails.application.config.content_security_policy do |policy|
policy.style_src :self, :unsafe_inlineRails compatibility
The gem is tested to work with Rails 3.2+ and Ruby 2.5.8+.
For Rails 2.3 and Ruby 1.8.7 support, use a version < 0.6.