Question

我正在尝试转换我的MongoDB聚合查询：

db.identification.aggregate([
    {
        $match: {
            userId: "b0e644d2-5a0c-4048-abea-6ae17c337e57"
        }
    },
    {
        $project: {
            status: {
                $objectToArray: "$status"
            }
        }
    },
    {
        $project: {
            status: {
                $arrayElemAt: ["$status.k", 0]
            }
        }
    },
    {
        $group: {
            _id: "$status",
            count: {$sum: 1}
        }
    },
    {
        $project: {
            _id: 0,
            status: {
                "name": "$_id",
                "count": "$count"
            }
        }
    },
    {
        $group: {
            _id: "counts",
            counts: {$addToSet: "$status"}
        }
    }
])

进入Scala DSL：

collection.aggregate(List(
      filter(Document("userId" -> userId)),
      project(Document("status" -> Document("$objectToArray" -> "$status"))),
      project(Document("status" -> Document("$arrayElemAt" -> List("$status.k" -> 0)))),
      group("$status", sum("count", 1)),
      project(Document("_id" -> 0, "status" -> Document("name" -> "$_id", "count" -> "$count"))),
      group("counts", addToSet("counts", "$status"))
    ))

但是，当我尝试运行查询时，出现以下错误：

com.mongodb.MongoCommandException: Command failed with error 168: 'Unrecognized expression '$status.k'' on server localhost:27017. The full response is { "ok" : 0.0, "errmsg" : "Unrecognized expression '$status.k'", "code" : 168, "codeName" : "InvalidPipelineOperator" }

有没有办法使用预定义的聚合查询，或者有人可以解释我在这里做错了什么？

Answer 1

看起来可以通过以下方式解决这个问题：

project(Document("status" -> Document("$arrayElemAt" -> List(BsonString("$status.k"), BsonInt32(0)))))

我希望能够提供更清洁的解决方案。看起来隐式转换无法正确处理Int。

Scala中的MongoDB聚合查询

1 个答案: