相关疑难解决方法(0)

我在mongodb中有一个md5的集合.我想找到所有重复的内容.md5列已编制索引.你知道使用map reduce做任何快速的方法吗？或者我应该迭代所有记录并手动检查重复项？

我目前使用map reduce的方法几乎两次迭代集合(假设重复数量非常少):

res = db.files.mapReduce(
    function () {
        emit(this.md5, 1);
    }, 
    function (key, vals) {
        return Array.sum(vals);
    }
)

db[res.result].find({value: {$gte:1}}).forEach(
function (obj) {
    out.duplicates.insert(obj)
});

Rails 4.2.5, Mongoid 5.1.0

我有三个型号- Mailbox,Communication和Message.

mailbox.rb

class Mailbox
    include Mongoid::Document
    belongs_to :user
    has_many :communications
end

communication.rb

class Communication
    include Mongoid::Document
    include Mongoid::Timestamps
    include AASM

    belongs_to :mailbox
    has_and_belongs_to_many :messages, autosave: true

    field :read_at,     type: DateTime
    field :box,         type: String
    field :touched_at,  type: DateTime
    field :import_thread_id, type: Integer
    scope :inbox, -> { where(:box => 'inbox') }
end

message.rb

class Message
    include Mongoid::Document
    include Mongoid::Timestamps

    attr_accessor :communication_id

    has_and_belongs_to_many :communications, autosave: true
    belongs_to :from_user, class_name: 'User'
    belongs_to …