Find not used Rails endpoints via BigQuery

a.rb

require 'bundler/inline'

gemfile do
  eval File.read(File.join(__dir__, 'Gemfile'))

  gem 'js_regex'
  gem 'pry-byebug'
end

require_relative 'config/environment'

data = Rails.application.routes.routes.group_by(&:verb).transform_values {|xs|
  xs.map {|x|
    {regexp: JsRegex.new(x.path.to_regexp).source, spec: x.path.spec.to_s}
  }
}
specs = data.values.flatten.map {|d| d[:spec] }.uniq

# Replace with your table name
# This script assumes the table has path and method column
log_table_name = 'project.dataset.table'

sql = <<~SQL
  CREATE TEMPORARY FUNCTION
    EXTRACT_SPEC(method STRING, path STRING)
    RETURNS STRING
    LANGUAGE js AS r"""
      const data = #{data.to_json};

      const result = (data[method] || []).find(r => new RegExp(r.regexp).exec(path));

      return result && result.spec;
    """;

  WITH specs AS (
    SELECT *
    FROM UNNEST(ARRAY<STRUCT<id INT64, name STRING>> [
      #{specs.map.with_index {|o, i| "(#{i}, #{o.dump})" }.join(',')}
    ])
  ),
  specs_with_count AS (
    SELECT EXTRACT_SPEC(method, path) AS spec, COUNT(*) AS count
    FROM `#{log_table_name}`
    GROUP BY spec
  )

  SELECT name FROM specs LEFT OUTER JOIN specs_with_count ON specs.name = specs_with_count.spec WHERE specs_with_count.count IS NULL
SQL

File.write('query.sql', sql)