我正在尝试从我的 seeds.rb 文件中执行这一行:

ActiveRecord::Base.connection.execute("UPDATE bairros SET created_at = (SELECT NOW());")

我名为“bairros”的表有 643k 行，一旦它在 rake db:seed 命令上到达这个文件，它就会抛出这个错误

    Mysql2::Error: Lost connection to MySQL server during query: UPDATE bairros SET created_at = (SELECT NOW());
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:286:in `query'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:286:in `block in execute'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:425:in `block in log'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activesupport-4.0.0/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:420:in `log'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:286:in `execute'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/connection_adapters/mysql2_adapter.rb:220:in `execute'
/home/ubuntu/projetos/AnuncieImoveis/releases/20131015210221/db/seeds.rb:48:in `<top (required)>'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:222:in `load'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:222:in `block in load'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:213:in `load_dependency'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:222:in `load'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/railties-4.0.0/lib/rails/engine.rb:540:in `load_seed'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/tasks/database_tasks.rb:153:in `load_seed'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/gems/activerecord-4.0.0/lib/active_record/railties/databases.rake:181:in `block (2 levels) in <top (required)>'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/bin/ruby_noexec_wrapper:14:in `eval'
/home/ubuntu/.rvm/gems/ruby-2.0.0-p195@thedoors/bin/ruby_noexec_wrapper:14:in `<main>'
Tasks: TOP => db:seed
(See full trace by running task with --trace)

我真的不知道如何解决这个问题。谁能帮帮我？

最佳答案

这个错误还有一个潜在的原因，那就是ActiveRecord连接池reaper .启用后，reaper 会扫描连接池中的“死”连接并关闭它们。在我的测试中，它似乎过于热心并且也关闭了完全活跃的连接(通常是运行稍大查询的连接)。

尝试从您的数据库配置中清除 reaping_frequency(将其关闭)，看看是否有帮助。扫描您的代码库以查找该字符串，并确保它未设置(或只是删除!)。如果您看到类似 config['reaping_frequency'] = ENV['DB_REAP_FREQ'] || 的行10，知道|| 10 实际上是设置一个较低的默认值 10s。这种模式在 Rails 代码库中存在了一段时间，直到更改为 reverted。由于它引起了各种问题，包括 killing long running queries , 但仍然是 recommended by Heroku .

如果禁用死神可以解决问题，我建议将其禁用。 Rails 不再默认设置它，它似乎导致的问题多于它解决的问题。

我遇到了和你一样的错误，我就是这样解决的。就个人而言，我将其禁用。我在 blog 上更详细地写了我的具体问题。 .

关于mysql - 尝试更新 mySQL 中的 640k 行得到 "Lost connection to MySQL server during query"，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19391526/