使用 PostgreSQL 运行 Rails 3,
我进行了迁移,更新了数百万条小记录。
Record.find_each do |r|
r.doing_incredibly_complex_stuff
r.save!
puts "#{r.id} updated"
end
由于我认为 ActiveRecord 将此类更新包装在事务中,因此“提交”时间很长,占用的内存也很大,而在上面的示例中,每条记录都已“打印”到屏幕上。
那么,我可以在事务之外运行这个 find_each 吗——虽然它很安全——节省大量“提交”时间和内存?
一种ActiveRecord::Base.without_transaction do ... ; 结束我猜:-)
或者:我错了,迁移没有包装到事务中,我看到的只是 SQL 更新语句应用?
编辑:似乎 threre 与事务没有链接,这是我中断迁移后得到的堆栈跟踪,当所有内容都打印在屏幕上并且 RAM 从 500MB 空闲减少到 ~30MB 时:
IRB::Abort: abort then interrupt!!
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activesupport-3.0.4/lib/active_support/whiny_nil.rb:46:in `call'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activesupport-3.0.4/lib/active_support/whiny_nil.rb:46:in `method_missing'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/connection_adapters/postgresql_adapter.rb:978:in `flatten'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/connection_adapters/postgresql_adapter.rb:978:in `block in select'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/connection_adapters/postgresql_adapter.rb:977:in `map'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/connection_adapters/postgresql_adapter.rb:977:in `select'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:7:in `select_all'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/connection_adapters/abstract/query_cache.rb:56:in `select_all'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/base.rb:467:in `find_by_sql'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/relation.rb:64:in `to_a'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/activerecord-3.0.4/lib/active_record/relation.rb:356:in `inspect'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/railties-3.0.4/lib/rails/commands/console.rb:44:in `start'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/railties-3.0.4/lib/rails/commands/console.rb:8:in `start'
from /Users/clement/.rvm/gems/ruby-1.9.2-p136@gemset/gems/railties-3.0.4/lib/rails/commands.rb:23:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
编辑(2):哇。结果发现它很长,因为 find_each 在迭代后返回所有元素。
我试过了 :
Record.tap do |record_class|
record_class.find_each do |r|
r.doing_incredibly_complex_stuff
r.save!
puts "#{r.id} updated"
end
end
=> Record(id: integer, ...)
所以它按预期立即归还了控制台。:)
但后来我仍然看到一个奇怪的行为:RAM 没有释放。相反,一旦我退出任期,RAM 仍然暴跌......
也许我的水龙头解决方案不令人满意?还是批量选择吗?在 find_each 之后如何避免批量选择?
谢谢!