Ruby on rails 是否仅在块中建立与另一个数据库的连接?
在rails应用程序中,我使用纯ruby编写了以下代码:Ruby on rails 是否仅在块中建立与另一个数据库的连接?,ruby-on-rails,ruby,Ruby On Rails,Ruby,在rails应用程序中,我使用纯ruby编写了以下代码: class LinkCreator attr_accessor :animal def initialize(animal:) @animal = animal end def call "something#{link_id}" end private def link_id connection.execute(sql_request).first.first end
class LinkCreator
attr_accessor :animal
def initialize(animal:)
@animal = animal
end
def call
"something#{link_id}"
end
private
def link_id
connection.execute(sql_request).first.first
end
def sql_request
"SELECT field FROM table WHERE field_id = '#{field_id}' LIMIT 1"
end
def field_id
animal.field_id
end
def connection
ActiveRecord::Base.establish_connection(
adapter: "mysql",
host: ENV["MYSQL_HOST"],
username: ENV["MYSQL_USERNAME"],
password: ENV["MYSQL_PASSWORD"],
database: ENV["MYSQL_DB_NAME"]
).connection
end
end
正如您所看到的,这不是一个模型,而是一个简单的类。问题在于,activerecord的连接发生了更改,其他请求随后在新连接上执行
是否可以仅在块中建立连接并返回到旧连接。我知道我可以建立另一个连接,但这对性能非常不利。使用实例变量存储连接可能会有所帮助。大概是这样的:
def connection
@connection ||= ActiveRecord::Base.establish_connection(
adapter: "mysql",
host: ENV["MYSQL_HOST"],
username: ENV["MYSQL_USERNAME"],
password: ENV["MYSQL_PASSWORD"],
database: ENV["MYSQL_DB_NAME"]
).connection
end
这样,在将来的连接尝试中检索现有连接,而不是建立新连接。如果您将所有数据库连接都保存在
数据库中,那就太好了。yml
development:
adapter: mysql2
other stuff...
db_2:
adapter: mysql2
other stuff..
other_envs:
.....
然后创建一个类
class OtherDB < ActiveRecord::Base
establish_connection(:db_2)
end
在这里查看我的博客您可以在块内执行一些查询。首先,定义一些扩展ActiveRecord的模块,如下所示。这是生产中使用的代码的一部分,用于根据每个请求更改数据库连接,以及临时切换数据库以在另一个数据库中执行某些查询
# RAILS_ROOT/lib/connection_switch.rb
module ConnectionSwitch
def with_db(connection_spec_name)
current_conf = ActiveRecord::Base.connection_config
begin
ActiveRecord::Base.establish_connection(db_configurations[connection_spec_name]).tap do
Rails.logger.debug "\e[1;35m [ActiveRecord::Base switched database] \e[0m #{ActiveRecord::Base.connection.current_database}"
end if database_changed?(connection_spec_name)
yield
ensure
ActiveRecord::Base.establish_connection(current_conf).tap do
Rails.logger.debug "\e[1;35m [ActiveRecord::Base switched database] \e[0m #{ActiveRecord::Base.connection.current_database}"
end if database_changed?(connection_spec_name, current_conf)
end
end
private
def database_changed?(connection_spec_name, current_conf = nil)
current_conf = ActiveRecord::Base.connection_config unless current_conf
current_conf[:database] != db_configurations[connection_spec_name].try(:[], :database)
end
def db_configurations
@db_config ||= begin
file_name = "#{Rails.root}/config/database.yml"
if File.exists?(file_name) || File.symlink?(file_name)
config ||= HashWithIndifferentAccess.new(YAML.load(ERB.new(File.read(file_name)).result))
else
config ||= HashWithIndifferentAccess.new
end
config
end
end
end
ActiveRecord.send :extend, ConnectionSwitch
现在,您可以按如下方式使用它:
ActiveRecord.with_db("db_connection_name") do
# some queries to another db
end
在Rails代码库中找到了最简短的示例,并稍作修改:
def with_another_db(another_db_config)
original_connection = ActiveRecord::Base.remove_connection
ActiveRecord::Base.establish_connection(another_db_config)
yield
ensure
ActiveRecord::Base.establish_connection(original_connection)
end
用法(假设您的数据库.yml
中有另一个\u db:部分):
我使用取自Heroku的
数据库\u URL
的环境变量连接到不同的数据库:
class Database
def self.development!
ActiveRecord::Base.establish_connection(:development)
end
def self.production!
ActiveRecord::Base.establish_connection(ENV['PRODUCTION_DATABASE'])
end
def self.staging!
ActiveRecord::Base.establish_connection(ENV['STAGING_DATABASE'])
end
end
e、 g:
如果您想连接到PostgresSQL,可以使用pgRubyGem&在块中添加以下代码
postgres = PG.connect :host => <host_name>, :port => <port>, :dbname => <database_name>, :user => <user>, :password => <password>
tables = postgres.exec(query)
tables.num_tuples.times do |i|
print tables[i]
end
db = Mysql2::Client.new ActiveRecord::ConnectionAdapters::ConnectionSpecification::ConnectionUrlResolver.new(<database_url>).to_hash
data = db.query(<<-SQL)
select * from students
SQL
print data
postgres=PG.connect:host=>,:port=>,:dbname=>,:user=>,:password=>
tables=postgres.exec(查询)
tables.num_tuples.times do|i|
打印表格[i]
结束
要在块内连接到mysql db,请使用mysql2 ruby gem&在块内添加以下代码
postgres = PG.connect :host => <host_name>, :port => <port>, :dbname => <database_name>, :user => <user>, :password => <password>
tables = postgres.exec(query)
tables.num_tuples.times do |i|
print tables[i]
end
db = Mysql2::Client.new ActiveRecord::ConnectionAdapters::ConnectionSpecification::ConnectionUrlResolver.new(<database_url>).to_hash
data = db.query(<<-SQL)
select * from students
SQL
print data
db=Mysql2::Client.new ActiveRecord::ConnectionAdapters::ConnectionSpecification::ConnectionUrlResolver.new()。到\u散列
data=db.query(Tryactive\u record\u slavegem:
这里的重要区别在于,连接是在所有普通对象的基类以外的对象上进行的,因此可以不使用与普通对象的连接。这也可以将配置保持在一个公共位置,并且我认为保持备用数据库连接打开,这对性能来说可能是一件好事mance,取决于您的使用条件。这段代码很好。您考虑过将其作为gem发布吗?@sufleR,不,我没有。也许这是值得的。@NoobieCorrect,这段代码不是线程安全的。更改ActiveRecord::Base connection会影响所有线程。您需要创建一个新的ActiveRecord::ConnectionAdapters::ConnectionPool
f或者附加数据库,然后您可以使用连接块将代码包装到my\u conn\u池中。
db = Mysql2::Client.new ActiveRecord::ConnectionAdapters::ConnectionSpecification::ConnectionUrlResolver.new(<database_url>).to_hash
data = db.query(<<-SQL)
select * from students
SQL
print data