Question

我有一个JSON数据，例如：

[
    {
        "_id": "5e887ee61c7f053dc8702214",
        "leadName": "Experienced",
        "leads": [
            {
                "name": "Joey",
                "mobile": 1524524678,
                "_id": "5e887ee61c7f053dc8702212",
                "leadType": "5e887a470962a53b80e0b57a"
            },
            {
                "name": "Ben",
                "mobile": 1524524678,
                "_id": "5e887ee61c7f053dc8702213",
                "leadType": "5e887a470962a53b80e0b57a"
            }
        ]
        "__v": 0
    },
    {
        "_id": "5e887fa91c7f053dc8702217",
        "leadName": "Fresher",
        "leads": [
            {
                "name": "Rachel",
                "mobile": 1524524678,
                "_id": "5e887fa91c7f053dc8702215",
                "leadType": "5e887a470962a53b80e0b578"
            },
            {
                "name": "Chandler",
                "mobile": 1524524678,
                "_id": "5e887fa91c7f053dc8702216",
                "leadType": "5e887a470962a53b80e0b57a"
            }
        ]
        "__v": 0
    }
]

属于leads数组的每个对象都有一个与其关联的leadType。 leadType是另一个架构的参考_id。我在这里尝试访问的是与作为请求传递的特定leadType匹配的所有对象/文档。

我有四分之三的用户有一个与leadType相关联的"leadType": "5e887a470962a53b80e0b57a"。

当我使用"leadType": "5e887a470962a53b80e0b57a"查询以检索这3个用户的详细信息时，它仅与对象的第一个数组中的单个用户匹配。和第二个对象数组中的一个。

我尝试了以下查询：

exports.leads_by_type = (req, res) => {
  const { leadtypeid } = req.body;

  Lead.find({"leads.leadType": leadtypeid}, {leads: { $elemMatch : {leadType: leadtypeid}}}, (err, result) => {
    res.json(result)
  });
  //this query returns only the first document of first object's array of objects and one from second.


  //OR EVEN THIS ONE       

  Lead.aggregate([
    {$match: {userId: req.user.userId}},
    {$unwind: "$leads"},
    {$match: {"leads.leadType": leadtypeid}}
  ], (err, test) => {
    res.json({test})
  });
  //this query returns empty array []

};

我需要返回一个或多个与给定ID匹配的每个文档。在SO和这个特定的问题Make $elemMatch (projection) return all objects that match criteria（看起来像我的用例）上，我尝试了很多方法，但是似乎都没有一个能解决我的问题。

请帮助解决此问题。这真的很重要。

Answer 1

您的第二个解决方案将返回一个空数组，因为您在第一个_id = leadtypeid中使用$match搜索文档，但是没有具有此ID的文档，我的意思是document是整个对象，有

_id = "5e887ee61c7f053dc8702214" or "5e887fa91c7f053dc8702217"

只要您只对leadtypeid感兴趣，那么我们可以将其添加到第一个$ match中，但这还不够，因为这将搜索具有该线索类型的文档，因此结果将包含你不想的第四领先这就是为什么我们使用$ unwind来在单独的文档中获取具有潜在顾客类型的每个文档的原因然后匹配所需的潜在客户类型，以摆脱第四种潜在客户类型

所以查询将是这样

注意：将'5e887a470962a53b80e0b57a'替换为leadtypeid

db.collectionName.aggregate(
    [
        {
            $match: {
                'leads.leadType': '5e887a470962a53b80e0b57a' // this to find all the documents which have this lead type
            }
        },
        {
            $unwind: '$leads' // to have multiple documents, each document with leads array of only one item in it, the lead type we are searching for only
        },
        {
            $match: {
                'leads.leadType': '5e887a470962a53b80e0b57a' // to get the documents that have this lead type and get rid of any other lead type
            }
        }
    ]
)

此查询的结果将为

{
    "_id" : "5e887ee61c7f053dc8702214",
    "leadName" : "Experienced",
    "leads" : {
        "name" : "Joey",
        "mobile" : 1524524678,
        "_id" : "5e887ee61c7f053dc8702212",
        "leadType" : "5e887a470962a53b80e0b57a"
    }
}
{
    "_id" : "5e887ee61c7f053dc8702214",
    "leadName" : "Experienced",
    "leads" : {
        "name" : "Ben",
        "mobile" : 1524524678,
        "_id" : "5e887ee61c7f053dc8702213",
        "leadType" : "5e887a470962a53b80e0b57a"
    }
}
{
    "_id" : "5e887fa91c7f053dc8702217",
    "leadName" : "Fresher",
    "leads" : {
        "name" : "Chandler",
        "mobile" : 1524524678,
        "_id" : "5e887fa91c7f053dc8702216",
        "leadType" : "5e887a470962a53b80e0b57a"
    }
}

希望这就是您要寻找的

无法使用$ elemMatch查找匹配的文档

1 个答案: