Question

我需要创建一个rake任务，从MySQL数据库获取表行，解析数据并插入Oracle数据库。数据库位于两个不同的主机上。

我目前的尝试：

namespace :import_from_mysql do
  class MySQLConnection < ActiveRecord::Base
    self.abstract_class = true
    establish_connection({
    :adapter  => 'mysql',
    :host     => 'xxx.xxx.com',
    :database => 'sample_database',
    :username => 'username',
    :password => 'password'
    })
  end

  class MySQLTable < MySQLConnection
    self.table_name = "users"
    self.primary_key = "id"
    self.inheritance_column = "something_unique_here"
  end

  desc "Parse data before inserting to oracle database"
  task :insert_to_oracle => :environment do |t|
    puts "Rake task has begun...\n\n"
    puts "Parsing data from MYSQL...\n\n"

    MySQLTable.establish_connection

    puts "Rake task has completed!"
  end
end

但 MySQLTable.establish_connection 建立了与本地数据库的连接，即使我正在尝试连接到mysql_adapter，也是sqlite。

当我尝试使用以下命令建立连接时，我能够连接到MySQL适配器，但我不知道在建立连接后如何访问我的表：

ActiveRecord::Base.establish_connection({:adapter => "mysql", :database => "sample_database", :host => "xxx.xxx.com", :username => "username", :password => "password" })

有关为何继续连接到sqlite的任何想法？在成功建立与mysql的连接后，如何在MySQLTable.establish_connection语句之后选择表行？

Answer 1

使用ActiveRecord :: Base生成连接，您可以针对连接的任何数据库执行SQL语句。像这样：

connection = ActiveRecord::Base.establish_connection(
  :adapter  => "mysql",
  :host     => "faraway",
  :username => "myuser",
  :password => "mypass",
  :database => "somedatabase"
)
connection.execute('SELECT * FROM users')

建立后，也可以从ActiveRecord :: Base类引用连接。

ActiveRecord::Base.establish_connection(...)
ActiveRecord::Base.connection.execute(...)

Answer 2

虽然我是一个连接和“数据库后台办公室”的菜鸟，但我的琐碎方法就像一个魅力，并且rake任务中不需要参数来更新仅包含定义数据的“域表”，例如合法或帮助文本：

pre_db = ActiveRecord::Base.establish_connection('preproduction').connection

prod_db = ActiveRecord::Base.establish_connection('online').connection

并在database.yml我定义了数据库。（“前期制作”是我个案中dev和prod之间的一个步骤，以及像“开发”这样的真实环境。其中'online'几乎与'production'相同（我出于安全原因做了一个不同的条目 - 不破坏生产如果上传database.yml

Answer 3

您可以在rake任务中使用mysql2 gem（https://github.com/brianmario/mysql2）。

client = Mysql2::Client.new(:host => "localhost", :username => "username", :database => "sample_database", :password => "password")
users = client.query("SELECT * FROM users")

Answer 4

认为它可能对其他人有帮助。以下对我有用！

connection = ActiveRecord::Base.establish_connection(
  :adapter  => "mysql",
  :host     => "faraway",
  :username => "myuser",
  :password => "mypass",
  :database => "somedatabase"
)

@connection = ActiveRecord::Base.connection
result = @connection.exec_query('SELECT * FROM users')

result.each do |row|
puts row
end

此处，用户是“somedatabase”中已存在的表。

如何从rake任务建立连接？

4 个答案: