无法从 Sequel gem 连接 mysql答案

【问题标题】：Unable to connect mysql from Sequel gem无法从 Sequel gem 连接 mysql
【发布时间】：2009-07-17 17:15:07
【问题描述】：

当我尝试从 Sequel 连接到 MySQL 时。我收到这些错误：

require 'rubygems'
        require 'sequel'
        DB = Sequel.connect(:adapter => 'mysql', :user => 'root', :host => 'localhost', :database => 'scanty',:password=>'xx')
        DB.tables
    Sequel::DatabaseConnectionError: NameError uninitialized constant Mysql::CLIENT_MULTI_RESULTS
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/adapters/mysql.rb:98:in `connect'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/database.rb:92:in `initialize'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/connection_pool.rb:166:in `call'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/connection_pool.rb:166:in `make_new'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/connection_pool.rb:153:in `available'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/connection_pool.rb:144:in `acquire'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/connection_pool.rb:143:in `synchronize'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/connection_pool.rb:143:in `acquire'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/connection_pool.rb:105:in `hold'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/database.rb:471:in `synchronize'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/adapters/mysql.rb:128:in `execute'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/dataset.rb:314:in `execute'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/adapters/mysql.rb:342:in `execute'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/adapters/mysql.rb:298:in `fetch_rows'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/dataset.rb:185:in `each'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/dataset/convenience.rb:156:in `map'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/dataset/convenience.rb:156:in `map'
        from /opt/local/lib/ruby/gems/1.8/gems/sequel-3.2.0/lib/sequel/adapters/shared/mysql.rb:60:in `tables'
        from (irb):6irb(main):007:0> Sequel::DatabaseConnectionError: NameErro

【问题讨论】：

您的错误似乎被截断了？另外，你的函数调用中的主机在哪里？
我添加了主机，但它仍然抛出同样的错误

标签： mysql ruby sequel

【解决方案1】：

需要安装原生的MySQL驱动，纯ruby的驱动不兼容Sequel。

根据您的 Ruby 安装，只需执行 gem install mysql 可能就足够了。但是，如果纯 Ruby mysql.rb 文件已经在您的 Ruby 加载路径中，您要么需要将其从加载路径中删除，要么在调用 Sequel.connect 之前使用 gem('mysql')。

【讨论】：

【解决方案2】：

您缺少:host=>'localhost' 或任何您的主机。

另外，这纯粹是出于性能原因，您应该尝试启用:compress。它可以节省大量带宽。

http://sequel.rubyforge.org/rdoc/files/doc/opening_databases_rdoc.html

编辑：好的，如果不是主机，可能是冲突？见http://groups.google.com/group/sequel-talk/browse_thread/thread/ee39640a92351f1?pli=1。还有http://www.mail-archive.com/sequel-talk@googlegroups.com/msg02275.html

【讨论】：

谢谢，我在机器上安装了两个版本的 mysql gem。