db-bloat.rake

namespace :db do
  namespace :bloat do
    desc 'Поиск распухших таблиц'
    task :tables => :environment do
      redis = Redis::Namespace.new('db:bloat')
      connection = ActiveRecord::Base.connection

      connection.tables.each do |table_name|
        begin
          rows_counted = redis.hget('tables', table_name)
          unless rows_counted
            rows_counted = connection.select_value("select count(*) from #{table_name}")
            redis.hset('tables', table_name, rows_counted)
          end
          rows_counted = rows_counted.to_i
          next if rows_counted.zero?

          rows_estimated = connection.
            select_value("select reltuples::int4 from pg_class where oid = 'public.#{table_name}'::regclass").
            to_i

          bloat = rows_estimated * 100 / rows_counted - 100

          if bloat > 25
            puts "#{table_name} > count: #{rows_counted}, estimate: #{rows_estimated}, bloat: #{bloat}"
            connection.execute "VACUUM ANALYZE #{table_name}"
          end
        rescue Exception => e
          puts e.message
        end
      end

      redis.expire('tables', 5.days)
    end

    desc 'Очистка кеша для распухших таблиц'
    task :clear_cache => :environment do
      Redis::Namespace.new('db:bloat').del('tables')
    end
  end
end