rails_explain_sql_initializer

explain.rb

class Explainer < ActiveSupport::LogSubscriber
  def sql(event)
    payload = event.payload
    return if ignore_payload?(payload)

    debug color(ActiveRecord::Base.connection.explain(payload[:sql], payload[:binds]), :yellow)
  end

  private

  IGNORED_PAYLOADS = %w[SCHEMA EXPLAIN].freeze
  EXPLAINED_SQLS = /\A\s*(with|select|update|delete|insert)\b/i.freeze

  def ignore_payload?(payload)
    payload[:cached] ||
      IGNORED_PAYLOADS.include?(payload[:name]) ||
      payload[:sql] !~ EXPLAINED_SQLS
  end
end

Explainer.attach_to :active_record