database size rake task

datasize.rake

# Run rake db:size to get a print of your database size in bytes.
# Run rake db:tables:size to get the sizes for individual tables
# Works for MySQL and PostgreSQL. Not tested elsewhere.

namespace :db do
  desc 'Print data size for entire database'
  task :size => :environment do

    database_name = ActiveRecord::Base.connection.instance_variable_get("@config")[:database]
    adapter = ActiveRecord::Base.connection.adapter_name.downcase
    case adapter
    when "mysql"
      sql = "select FORMAT(SUM(data_length + index_length), 0) as bytes from information_schema.TABLES where table_schema = '#{database_name}'"
      puts ActiveRecord::Base.connection.execute(sql).fetch_hash.values.first
    when "postgres", "postgresql"
      sql = "SELECT pg_size_pretty(pg_database_size('#{database_name}'));"
      puts ActiveRecord::Base.connection.execute(sql)[0]["pg_size_pretty"]
    when "oracle", "oci"
      sql = "select a.data_size+b.temp_size+c.redo_size+d.controlfile_size  from ( select sum(bytes) data_size from dba_data_files) a, ( select nvl(sum(bytes),0) temp_size from dba_temp_files ) b, ( select sum(bytes) redo_size from sys.v_$log ) c, ( select sum(BLOCK_SIZE*FILE_SIZE_BLKS) controlfile_size from v$controlfile) d;"
      puts ActiveRecord::Base.connection.execute(sql).fetch_hash.values.first
    else
      raise "#{adapter} is not supported"
    end
  end

  namespace :tables do
    desc 'Print data size for all tables'
    task :size => :environment do

      database_name = ActiveRecord::Base.connection.instance_variable_get("@config")[:database]
      adapter = ActiveRecord::Base.connection.adapter_name.downcase
      case adapter
      when "mysql"
        sql = "select TABLE_NAME, FORMAT((data_length + index_length), 0) as bytes from information_schema.TABLES where table_schema = '#{database_name}' ORDER BY (data_length + index_length) DESC"
        result = ActiveRecord::Base.connection.execute(sql)
        while (row = result.fetch_hash) do
          puts "#{row['TABLE_NAME']} #{row['bytes']}"
        end
      when "postgres", "postgresql"
        sql = "SELECT tablename FROM pg_tables WHERE schemaname = 'public' ORDER BY tablename;"
        tables = ActiveRecord::Base.connection.execute(sql)
        tables.each do |table|
          name = table['tablename']
          sql = "SELECT pg_size_pretty(pg_total_relation_size('#{name}'));"
          res = ActiveRecord::Base.connection.execute(sql)
          puts "#{name} #{res[0]['pg_size_pretty']}"
        end
      else
        raise "#{adapter} is not supported"
      end
    end
  end
end