创建聚合管道时 AccumulatorOperators Max 出现问题

Question

我正在尝试将以下 Mongo shell 聚合查询转换为 Spring 数据 MongoDB 聚合：

db.getCollection('Orders').aggregate([
{ $group: {
    "_id": {"book":"$bookingId"},
    "docs": {$push: '$$ROOT'}
  }
},
{$project: {
   latestOrd: {
      $filter: {
         input: "$docs",
         as: "item",
         cond: { $eq: ["$$item.bookingVersion", { $max: "$docs.bookingVersion" }] }
      }
   }
 }
},
{ $unwind: "$latestOrd" },
{ $replaceRoot:{newRoot:"$latestOrd"}}
])

查询获取所有预订版本最高的订单（例如，一个预订 ID 可能有许多版本为 3 的文档）。

此查询在 Mongo shell 中运行良好，但我对 Spring 的数据版本有疑问：

Aggregation.group("bookingId").push(Aggregation.ROOT).as("docs");
Aggregation.project().and(filter("docs")
          .as("item")
          .by(valueOf("item.bookingVersion")
                .equalToValue(AccumulatorOperators.Max.maxOf("docs.bookingVersion"))))
          .as("latestOrd");
Aggregation.unwind("latestOrd");
Aggregation.replaceRoot("latestOrd");

Spring 生成 Mongo 查询类似于我在上面提供的查询，除了 $max accumulator:

{ "$max" : "$$docs.bookingVersion" }

出于某种原因，它添加了双美元符号而不是单美元符号，结果我出现了以下错误：

'Use of undefined variable: docs' on server 127.0.0.1:27017

我正在使用 spring-boot-starter 2.1.0.RELEASE 和 Mongo 服务器的 4.2 版本。感谢您对此提供的任何帮助。

输入文件：

[
  {
    "_id": "5f847811ebcd1a51a0196736",
    "status": "REJECTED",
    "bookingId": "1",
    "bookingVersion": 4,
    "operation": "CREATE"
  },
  {
    "_id": "5f847811ebcd1a51a0196735",
    "status": "CREATED",
    "bookingId": "1",
    "bookingVersion": 4,
    "docNumber": "7",
    "operation": "CREATE"
  },
  {
    "_id": "5f847811ebcd1a51a0196734",
    "status": "CREATED",
    "bookingId": "1",
    "bookingVersion": 3,
    "docNumber": "6",
    "operation": "CREATE"
  },
  {
    "_id": "5f847811ebcd1a51a0196738",
    "status": "CREATED",
    "bookingId": "2",
    "bookingVersion": 1,
    "docNumber": "8",
    "operation": "CREATE"
  },
  {
    "_id": "5f847811ebcd1a51a0196737",
    "status": "CREATED",
    "bookingId": "2",
    "bookingVersion": 2,
    "docNumber": "9",
    "operation": "CREATE"
  }
]

预期输出：

[
  {
    "_id": "5f847811ebcd1a51a0196736",
    "status": "REJECTED",
    "bookingId": "1",
    "bookingVersion": 4,
    "operation": "CREATE"
  },
  {
    "_id": "5f847811ebcd1a51a0196735",
    "status": "CREATED",
    "bookingId": "1",
    "bookingVersion": 4,
    "docNumber": "7",
    "operation": "CREATE"
  },
  {
    "_id": "5f847811ebcd1a51a0196737",
    "status": "CREATED",
    "bookingId": "2",
    "bookingVersion": 2,
    "docNumber": "9",
    "operation": "CREATE"
  }
]

Answer 1

问题可能与 2.1.0.RELEASE 版本的 spring 引导有关，但升级它对我来说不是一个选项。为了完成这项工作，我创建了 AggregationExpression 而不是 AccumulatorOperators.Max.maxOf("docs.bookingVersion") 部分。

这里有一个方法：

  private AggregationExpression buildMaxExpression() {
    return new AggregationExpression() {
      @Override
      public Document toDocument(final AggregationOperationContext context) {
        return new Document("$max", "$docs.bookingVersion");
      }
    };
  }

创建聚合管道时 AccumulatorOperators Max 出现问题

Issue with AccumulatorOperators Max when creating aggregation pipeline

java

mongodb

spring-data

spring-data-mongodb

spring-mongodb