Question

我有两个集合作为bellow产品有用户参考。我按名称搜索产品＆amp;作为回报，我想使用map reduce方法将产品和用户的输出结合起来

user collection
{
  "_id" : ObjectId("52ac5dd1fb670c2007000000"),
  "company" : {
    "about" : "This is textile machinery dealer",
    "contactAddress" : [{
        "address" : "abcd",
        "city" : "52ac4bc6fb670c1007000000",
        "zipcode" : "39as46as80"
      },{
        "address" : "abcd",
        "city" : "52ac4bc6fb670c1007000000",
        "zipcode" : "39as46as80"
      }],
    "fax" : "58784868",
    "mainProducts" : "ads,asd,asd",
    "mobileNumber" : "9537236588",
    "name" : "krishna steels",
    }
  "user" : ObjectId("52ac4eb7fb670c0c07000000")
}

product colletion
{
  "_id" : ObjectId("52ac5722fb670cf806000002"),
  "category" : "52a2a9cc48a508b80e00001d",
  "deliveryTime" : "10 days after received the ",
  "price" : {
    "minPrice" : "2000",
    "maxPrice" : "3000",
    "perUnit" : "5288ac6f7c104203e0976851",
    "currency" : "INR"
  },
  "productName" : "New Mobile Solar Charger with Carabiner",
  "rejectReason" : "",
  "status" : 1,
  "user" : ObjectId("52ac4eb7fb670c0c07000000")
}

Answer 1

这不可能。 Mongo仅在一个集合上支持Map Reduce。您可以尝试在java集合中获取和合并。几天后我用java集合解决了类似的问题。

Click to see similar response about joins and multi collection not supported in mongo

Answer 2

这可以使用两个map reduce来完成。

你运行你的第一个MR然后你reduce将第二个MR运行到第一个MR的结果上。

你不应该这样做。 JOIN并非旨在通过MR完成，实际上听起来你正试图用inline输出这个MR，这本身就是一个非常糟糕的主意。

MR 不旨在内联到应用程序。

你最好在其他地方做JOIN。

想要使用map reduce在mongo db中合并两个集合

2 个答案: