MongoDb 从文档中删除子文档

Question

我有一个包含以下数据的集合:

{

  "_id" : ObjectId("4e3951905e746b3805000000"),
  "m" : "hello",
  "r" : [{
      "_id" : ObjectId("4e3951965e746b8007000000"),
      "u" : 3,
      "m" : "response1"
    }, {
      "_id" : ObjectId("4e39519d5e746bc00f000000"),
      "u" : 3,
      "m" : "response2"
    }, {
      "_id" : ObjectId("4e3953dc5e746b5c07000000"),
      "u" : 3,
      "m" : "response3"
    }, {
      "_id" : ObjectId("4e3953ea5e746bd40f000001"),
      "u" : 3,
      "m" : "response"
    }],
  "u" : 3,
  "w" : 3
}
{
  "_id" : ObjectId("4e3952c75e746bd807000001"),
  "m" : "asdfa",
  "r" : [{
      "_id" : ObjectId("4e39544e5e746bc00f000001"),
      "u" : 3,
      "m" : "response5"
    }],
  "u" : 3,
  "w" : 3
}

谁能建议如何从 'r' 键中删除子文档只有子文档的 id，我要删除？

例如，我想删除 id 为 4e39519d5e746bc00f000000 的子文档所以这个子文档应该被删除

{
  "_id" : ObjectId("4e39519d5e746bc00f000000"),
  "u" : 3,
  "m" : "response2"
},

Answer 1

很简单，你只需要使用$pull运营商:

db.items.update( {}, 
{ $pull : { r : {"_id": ObjectId("4e39519d5e746bc00f000000")} } }, false, false )