条件聚合阶段

Question

我们有 3 个集合来跟踪一个机械车间。
PARTS 根据 shopID
给出商品总数我们需要确认 INPROCESS 和 REJECT 中的商品总和是否等于 PARTS 中商店的数量。

但是，我们会去研究 REJECT - 仅当 INPROCESS 不等于计数时，从而节省查找。

如何实现。

PARTS

{
    "_id": ObjectId("xxxxxx"),
    "shop": "Q4",
    "count": 200,
}


INPROCESS

{
    "_id": ObjectId("xxxxxx"),
    "shop": "Q4",
    "itemID": "5647",
},
{
    "_id": ObjectId("xxxxxx"),
    "shop": "Q4",
    "itemID": "2314",
},


REJECTED

{
    "_id": ObjectId("xxxxxx"),
    "shop": "Q4",
    "itemID": "xxxx",
},
{
    "_id": ObjectId("xxxxxx"),
    "shop": "Q4",
    "itemID": "yyyy",
},

Answer 1

试试这个：

db.PARTS.aggregate([
  {
    $lookup: {
      from: "INPROCESS",
      localField: "shop",
      foreignField: "shop",
      as: "inprocess"
    }
  },
  {
    $match: {
      $expr: {
        $ne: [
          "$count",
          {
            $size: "$inprocess"
          }
        ]
      }
    }
  },
  {
    $lookup: {
      from: "REJECTED",
      localField: "shop",
      foreignField: "shop",
      as: "rejected"
    }
  },
  {
    $match: {
      $expr: {
        $ne: [
          "$count",
          {
            $add: [
              {
                $size: "$inprocess"
              },
              {
                $size: "$rejected"
              }
            ]
          }
        ]
      }
    }
  }
])

MongoPlayground

条件聚合阶段

Conditional aggregation stage

aggregation-framework

mongodb4.0