Rails
rake

Railsで複数DBとうまく付合おう

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前提条件

自社で使っているDBのシステム上、管理ツールで使っているデータとサービス側で集計したログのレポートデータを別のDBで管理したい

そのため、migrateディレクトリがmigrate と report_migrateと2つ存在する

スクリーンショット 2016-12-25 18.46.30.png


問題

rake db:migrate を実行すると、hoge-admin(migrateディレ)のDBにしか適応しない


解決策

まずは、 ちょうどいいgemがないかどうかを探しても出てこないので、自分でなんとかするしかなかった

ヒントはないかと探すと、

/vendor/bundle/ruby/2.2.0/gems/activerecord-4.2.4/lib/active_record/migration.rb

の中に、実行内容が書かれているので、それを元に、自分でrakeタスクを作成することにした

そのコードが以下


lib/tasks/db.rake

%w(

report
)
.each do |db_prefix|
%w(
create:all
create
drop:all
drop
purge:all
purge
migrate
_dump

migrate:reset
migrate:status

reset
abort_if_pending_migrations
setup

schema:dump
schema:load
schema:load_if_ruby
schema:cache:dump
schema:cache:clear

structure:dump
structure:load

test:deprecated
test:load
test:load_structure
test:clone
test:clone_schema
test:clone_structure
).each do |task_name|
task = Rake::Task["db:#{task_name}"]
next unless task
task.enhance do
next if ENV["PRIMARY_ONLY"] == "true"
env = ENV["RAILS_ENV"] ||= "development"
config_name = [db_prefix, env].join("_")

old_config = ActiveRecord::Base.configurations
ActiveRecord::Base.configurations =
{env => ActiveRecord::Base.configurations[config_name]}
ActiveRecord::Migrator.migrations_paths =
[[Rails.root, "db", "#{db_prefix}_migrate"].join("/")]
ActiveRecord::Tasks::DatabaseTasks.migrations_paths =
[[Rails.root, "db", "#{db_prefix}_migrate"].join("/")]
ActiveRecord::Tasks::DatabaseTasks.db_dir =
[Rails.root, "db", "#{db_prefix}_migrate"]
ActiveRecord::Base.establish_connection(
ActiveRecord::Base.configurations[
ActiveRecord::Tasks::DatabaseTasks.env])

Rake::Task["multi_db:#{task_name}"].invoke

ActiveRecord::Base.configurations = old_config
ActiveRecord::Migrator.migrations_paths =
[[Rails.root, "db", "migrate"].join("/")]
ActiveRecord::Tasks::DatabaseTasks.migrations_paths =
[[Rails.root, "db", "migrate"].join("/")]
ActiveRecord::Tasks::DatabaseTasks.db_dir =
[Rails.root, "db"]
ActiveRecord::Base.establish_connection(
ActiveRecord::Base.configurations[
ActiveRecord::Tasks::DatabaseTasks.env])
end
end
end


まずは、必要なタスクを書き出し、prefixをつけたmigrateを実行する。でも、そのままだと元々の

migrateが実行されなくなるので、元に戻す。

あとは、実際に実行するタスクの具体も定義する必要がある。それが以下のファイル


multi_db.rake

db_namespace = namespace :multi_db do

task :load_config do
puts ActiveRecord::Migrator.migrations_paths
unless ActiveRecord::Migrator.migrations_paths ==
[["db", "migrate"].join("/")]
next
end
env = ENV['RAILS_ENV'] ||= 'development'
db_prefix = ENV['DB_PREFIX']
raise "DB_PREFIX is needed" if db_prefix.nil?

config_name = [db_prefix, env].join("_")

ActiveRecord::Base.configurations = {
env => ActiveRecord::Base.configurations[env],
config_name => ActiveRecord::Base.configurations[config_name]
}
ActiveRecord::Migrator.migrations_paths = [[Rails.root, "db", "#{db_prefix}_migrate"].join("/")]
ActiveRecord::Tasks::DatabaseTasks.migrations_paths = [[Rails.root, "db", "#{db_prefix}_migrate"].join("/")]
ActiveRecord::Tasks::DatabaseTasks.db_dir = [Rails.root, "db", "#{db_prefix}_migrate"]
ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[config_name])
end

namespace :create do
task :all => [:load_config] do
ActiveRecord::Tasks::DatabaseTasks.create_all
end
end

desc 'Creates the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:create:all to create all databases in the config). Without RAILS_ENV it defaults to creating the development and test databases.'
task :create => [:load_config] do
ActiveRecord::Tasks::DatabaseTasks.create_current
end

namespace :drop do
task :all => [:load_config] do
ActiveRecord::Tasks::DatabaseTasks.drop_all
end
end

desc 'Drops the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:drop:all to drop all databases in the config). Without RAILS_ENV it defaults to dropping the development and test databases.'
task :drop => [:load_config] do
ActiveRecord::Tasks::DatabaseTasks.drop_current
end

namespace :purge do
task :all => [:load_config] do
ActiveRecord::Tasks::DatabaseTasks.purge_all
end
end

# desc "Empty the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:drop:all to drop all databases in the config). Without RAILS_ENV it defaults to purging the development and test databases."
task :purge => [:load_config] do
ActiveRecord::Tasks::DatabaseTasks.purge_current
end

desc "Migrate the database (options: VERSION=x, VERBOSE=false, SCOPE=blog)."
task :migrate => [:environment, :load_config] do
ActiveRecord::Tasks::DatabaseTasks.migrate
db_namespace['_dump'].invoke
end

# IMPORTANT: This task won't dump the schema if ActiveRecord::Base.dump_schema_after_migration is set to false
task :_dump do
if ActiveRecord::Base.dump_schema_after_migration
case ActiveRecord::Base.schema_format
when :ruby then db_namespace["schema:dump"].invoke
when :sql then db_namespace["structure:dump"].invoke
else
raise "unknown schema format #{ActiveRecord::Base.schema_format}"
end
end
# Allow this task to be called as many times as required. An example is the
# migrate:redo task, which calls other two internally that depend on this one.
db_namespace['_dump'].reenable
end

namespace :migrate do
# desc 'Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x).'
task :redo => [:environment, :load_config] do
if ENV['VERSION']
db_namespace['migrate:down'].invoke
db_namespace['migrate:up'].invoke
else
db_namespace['rollback'].invoke
db_namespace['migrate'].invoke
end
end

# desc 'Resets your database using your migrations for the current environment'
task :reset => ['db:drop', 'db:create', 'db:migrate']

# desc 'Runs the "up" for a given migration VERSION.'
task :up => [:environment, :load_config] do
version = ENV['VERSION'] ? ENV['VERSION'].to_i : nil
raise 'VERSION is required' unless version
ActiveRecord::Migrator.run(:up, ActiveRecord::Migrator.migrations_paths, version)
db_namespace['_dump'].invoke
end

# desc 'Runs the "down" for a given migration VERSION.'
task :down => [:environment, :load_config] do
version = ENV['VERSION'] ? ENV['VERSION'].to_i : nil
raise 'VERSION is required - To go down one migration, run db:rollback' unless version
ActiveRecord::Migrator.run(:down, ActiveRecord::Migrator.migrations_paths, version)
db_namespace['_dump'].invoke
end

desc 'Display status of migrations'
task :status => [:environment, :load_config] do
unless ActiveRecord::SchemaMigration.table_exists?
abort 'Schema migrations table does not exist yet.'
end
db_list = ActiveRecord::SchemaMigration.normalized_versions

file_list =
ActiveRecord::Migrator.migrations_paths.flat_map do |path|
# match "20091231235959_some_name.rb" and "001_some_name.rb" pattern
Dir.foreach(path).grep(/^(\d{3,})_(.+)\.rb$/) do
version = ActiveRecord::SchemaMigration.normalize_migration_number($1)
status = db_list.delete(version) ? 'up' : 'down'
[status, version, $2.humanize]
end
end

db_list.map! do |version|
['up', version, '********** NO FILE **********']
end
# output
puts "\ndatabase: #{ActiveRecord::Base.connection_config[:database]}\n\n"
puts "#{'Status'.center(8)} #{'Migration ID'.ljust(14)} Migration Name"
puts "-" * 50
(db_list + file_list).sort_by { |_, version, _| version }.each do |status, version, name|
puts "#{status.center(8)} #{version.ljust(14)} #{name}"
end
puts
end
end

desc 'Rolls the schema back to the previous version (specify steps w/ STEP=n).'
task :rollback => [:environment, :load_config] do
step = ENV['STEP'] ? ENV['STEP'].to_i : 1
ActiveRecord::Migrator.rollback(ActiveRecord::Migrator.migrations_paths, step)
db_namespace['_dump'].invoke
end

# desc 'Pushes the schema to the next version (specify steps w/ STEP=n).'
task :forward => [:environment, :load_config] do
step = ENV['STEP'] ? ENV['STEP'].to_i : 1
ActiveRecord::Migrator.forward(ActiveRecord::Migrator.migrations_paths, step)
db_namespace['_dump'].invoke
end

# desc 'Drops and recreates the database from db/schema.rb for the current environment and loads the seeds.'
task :reset => [:environment, :load_config] do
db_namespace["drop"].invoke
db_namespace["setup"].invoke
end

# desc "Retrieves the charset for the current environment's database"
task :charset => [:environment, :load_config] do
puts ActiveRecord::Tasks::DatabaseTasks.charset_current
end

# desc "Retrieves the collation for the current environment's database"
task :collation => [:environment, :load_config] do
begin
puts ActiveRecord::Tasks::DatabaseTasks.collation_current
rescue NoMethodError
$stderr.puts 'Sorry, your database adapter is not supported yet. Feel free to submit a patch.'
end
end

desc 'Retrieves the current schema version number'
task :version => [:environment, :load_config] do
puts "Current version: #{ActiveRecord::Migrator.current_version}"
end

# desc "Raises an error if there are pending migrations"
task :abort_if_pending_migrations => :environment do
pending_migrations = ActiveRecord::Migrator.open(ActiveRecord::Migrator.migrations_paths).pending_migrations

if pending_migrations.any?
puts "You have #{pending_migrations.size} pending #{pending_migrations.size > 1 ? 'migrations:' : 'migration:'}"
pending_migrations.each do |pending_migration|
puts ' %4d %s' % [pending_migration.version, pending_migration.name]
end
abort %{Run `rake db:migrate` to update your database then try again.}
end
end

desc 'Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the database first)'
task :setup => ['db:schema:load_if_ruby', 'db:structure:load_if_sql', :seed]

desc 'Load the seed data from db/seeds.rb'
task :seed do
db_namespace['abort_if_pending_migrations'].invoke
ActiveRecord::Tasks::DatabaseTasks.load_seed
end

namespace :schema do
desc 'Create a db/schema.rb file that is portable against any DB supported by AR'
task :dump => [:environment, :load_config] do
require 'active_record/schema_dumper'
filename = ENV['SCHEMA'] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, 'schema.rb')
File.open(filename, "w:utf-8") do |file|
ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
end
db_namespace['schema:dump'].reenable
end

desc 'Load a schema.rb file into the database'
task :load => [:environment, :load_config] do
ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:ruby, ENV['SCHEMA'])
end

task :load_if_ruby => ['db:create', :environment] do
db_namespace["schema:load"].invoke if ActiveRecord::Base.schema_format == :ruby
end

namespace :cache do
desc 'Create a db/schema_cache.dump file.'
task :dump => [:environment, :load_config] do
con = ActiveRecord::Base.connection
filename = File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema_cache.dump")

con.schema_cache.clear!
con.tables.each { |table| con.schema_cache.add(table) }
open(filename, 'wb') { |f| f.write(Marshal.dump(con.schema_cache)) }
end

desc 'Clear a db/schema_cache.dump file.'
task :clear => [:environment, :load_config] do
filename = File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema_cache.dump")
FileUtils.rm(filename) if File.exist?(filename)
end
end

end

namespace :structure do
desc 'Dump the database structure to db/structure.sql. Specify another file with DB_STRUCTURE=db/my_structure.sql'
task :dump => [:environment, :load_config] do
filename = ENV['DB_STRUCTURE'] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "structure.sql")
current_config = ActiveRecord::Tasks::DatabaseTasks.current_config
ActiveRecord::Tasks::DatabaseTasks.structure_dump(current_config, filename)

if ActiveRecord::Base.connection.supports_migrations? &&
ActiveRecord::SchemaMigration.table_exists?
File.open(filename, "a") do |f|
f.puts ActiveRecord::Base.connection.dump_schema_information
f.print "\n"
end
end
db_namespace['structure:dump'].reenable
end

desc "Recreate the databases from the structure.sql file"
task :load => [:load_config] do
ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:sql, ENV['DB_STRUCTURE'])
end

task :load_if_sql => ['db:create', :environment] do
db_namespace["structure:load"].invoke if ActiveRecord::Base.schema_format == :sql
end
end

namespace :test do

task :deprecated do
Rake.application.top_level_tasks.grep(/^db:test:/).each do |task|
$stderr.puts "WARNING: #{task} is deprecated. The Rails test helper now maintains " \
"your test schema automatically, see the release notes for details."
end
end

# desc "Recreate the test database from the current schema"
task :load => %w(db:test:purge) do
case ActiveRecord::Base.schema_format
when :ruby
db_namespace["test:load_schema"].invoke
when :sql
db_namespace["test:load_structure"].invoke
end
end

# desc "Recreate the test database from an existent schema.rb file"
task :load_schema => %w(db:test:purge) do
begin
should_reconnect = ActiveRecord::Base.connection_pool.active_connection?
ActiveRecord::Schema.verbose = false
ActiveRecord::Tasks::DatabaseTasks.load_schema_for ActiveRecord::Base.configurations['test'], :ruby, ENV['SCHEMA']
ensure
if should_reconnect
ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[ActiveRecord::Tasks::DatabaseTasks.env])
end
end
end

# desc "Recreate the test database from an existent structure.sql file"
task :load_structure => %w(db:test:purge) do
ActiveRecord::Tasks::DatabaseTasks.load_schema_for ActiveRecord::Base.configurations['test'], :sql, ENV['SCHEMA']
end

# desc "Recreate the test database from a fresh schema"
task :clone => %w(db:test:deprecated environment) do
case ActiveRecord::Base.schema_format
when :ruby
db_namespace["test:clone_schema"].invoke
when :sql
db_namespace["test:clone_structure"].invoke
end
end

# desc "Recreate the test database from a fresh schema.rb file"
task :clone_schema => %w(db:test:deprecated db:schema:dump db:test:load_schema)

# desc "Recreate the test database from a fresh structure.sql file"
task :clone_structure => %w(db:test:deprecated db:structure:dump db:test:load_structure)

# desc "Empty the test database"
task :purge => %w(environment) do
ActiveRecord::Tasks::DatabaseTasks.purge ActiveRecord::Base.configurations['test']
end

# desc 'Check for pending migrations and load the test schema'
task :prepare => %w(environment) do
unless ActiveRecord::Base.configurations.blank?
db_namespace['test:load'].invoke
end
end
end
end


実行する範囲によって、ここまで定義しなくても良いかもしれないが、とりあえずこれで、rake db:migrateを実行することができるようになった