Simple script to find missing unique constrains for uniqueness validations in rails

find_missing_indices.rb

# run from the root: ruby find_missing_indices.rb
require File.expand_path("../config/environment", __FILE__)

Rails.application.eager_load!

models = ActiveRecord::Base.descendants
conn = ActiveRecord::Base.connection
missing_index = []

models.each do |model|
  uniqueness_validators = model.validators.select {|v| v.class == ActiveRecord::Validations::UniquenessValidator }

  uniqueness_validators.each do |validation|
    attrs = validation.attributes.dup
    attrs.concat Array(validation.options[:scope]) if validation.options.key? :scope
    attrs = attrs.map(&:to_s).map { |attr| model.column_names.include?(attr) ? attr : "#{attr}_id" }.sort

    unique_indices = conn.indexes(model.table_name).select { |idx| idx.unique }
    unless unique_indices.any? { |idx| idx.columns.sort == attrs }
      missing_index << [model, validation]
    end
  end
end

puts "=== Missing indices ==="
missing_index.each do |(model, validation)|
  msg = "#{model}: validates #{validation.attributes}"
  msg << " (scope: #{validation.options[:scope]})" if validation.options.key? :scope
  puts msg
end