Ruby Rails 4和Mongo DB 4.x在“；“大”；收集

有了Mongo支持的模型和大约800-900条记录，我正试图迭代并使用一些属性生成CSV

看起来是这样的：

each do |car|
  csv << columns.map { |column| car.__send__(column) }
end

A Moped::Errors::QueryFailure occurred in cars#index:

  The operation: #<Moped::Protocol::Query
  @length=94
  @request_id=376
  @response_to=0
  @op_code=2004
  @flags=[]
  @full_collection_name="app555555.cars"
  @skip=0
  @limit=0
  @selector={"$query"=>{}, "$orderby"=>{"created_at"=>-1}}
  @fields=nil>
failed with error 10128: "too much data for sort() with no index.  add an index or specify a smaller limit"

See https://github.com/mongodb/mongo/blob/master/docs/errors.md
for details about this error.
  app/models/car.rb:84:in `block in to_csv'

每辆车|
csv您可能缺少索引。这里有更多关于在mongo DB中添加索引的内容，谢谢grimsock，我已经在默认顺序列中添加了索引（它是在

创建的），并且可以正常工作！