MongoTemplate 聚合返回“IllegalArgumentException：无效引用”

Question

给定一个包含以下文档的集合：

{
    "_id": {
        "$oid": "5e8f83289d3a48132e9b6e34"
    },
    "resource-id": "my-default-network-map",
    "uri": "http://alto.example.com/networkmap",
    "mappings": [
       {
        "version-tag": "X",
        "address-aggregations": [{
            "pid": "PID1",
            "ipv4-addresses": ["192.0.2.0/24", "198.51.100.0/25"]
        }, {
            "pid": "PID2",
            "ipv4-addresses": ["198.51.100.128/25"]
        }, {
            "pid": "PID3",
            "ipv4-addresses": ["0.0.0.0/0"],
            "ipv6-addresses": ["::/0"]
        }]
       }, 
       {
        "version-tag": "Y",
        "address-aggregations": [{
            "pid": "PID1",
            "ipv4-addresses": ["192.0.2.0/24", "198.51.100.0/25"]
        }, {
            "pid": "PID2",
            "ipv4-addresses": ["198.51.100.128/25"]
        }]
       }],
    "_class": "com.example.restservice.entity.NetworkMapEntity"
}

并假设更多这些文档与其他“resource-id”值一起存在，我希望返回我之前键入的相同文档，但“mappings”数组仅包含具有 version-tag = X 和“ address-aggregations" 数组仅包含 [pidx,pidy,...] 中带有 "pid" 的对象。我目前能想到的最好的方法是以下聚合管道：

[
  {
    '$match': {
      'resource-id': 'my-default-network-map'
    }
  }, {
    '$unwind': {
      'path': '$mappings'
    }
  }, {
    '$match': {
      'mappings.version-tag': 'X'
    }
  }, {
    '$unwind': {
      'path': '$mappings.address-aggregations'
    }
  }, {
    '$match': {
      'mappings.address-aggregations.pid': {
        '$in': [
          'PID1', 'PID2'
        ]
      }
    }
  }, {
    '$group': {
      '_id': '$_id', 
      'resource-id': {
        '$first': '$resource-id'
      }, 
      'uri': {
        '$first': '$uri'
      }, 
      'version-tag': {
        '$first': '$mappings.version-tag'
      }, 
      'address-aggregations': {
        '$push': '$mappings.address-aggregations'
      }
    }
  }, {
    '$project': {
      '_id': 1, 
      'resource-id': 1, 
      'uri': 1, 
      'mappings.version-tag': '$version-tag', 
      'mappings.address-aggregations': '$address-aggregations'
    }
  }, {
    '$group': {
      '_id': '$_id', 
      'resource-id': {
        '$first': '$resource-id'
      }, 
      'uri': {
        '$first': '$uri'
      }, 
      'mappings': {
        '$push': '$mappings'
      }
    }
  }
]

在 mongodb 客户端 shell 上返回了预期的结果。但是，当我将此类对象转换为带有 Aggregation 对象的 MongoTemplate 查询时：

Aggregation aggregation = newAggregation(
  match(Criteria.where("resource-id").is(resourceId)),
  unwind("mappings"),
  match(Criteria.where("mappings.version-tag").is(versionTag)),
  unwind("mappings.address-aggregations"),
  match(Criteria.where("mappings.address-aggregations.pid").in(pids)),
  group("$_id")
    .first("resource-id").as("resource-id")
    .first("uri").as("uri")
    .first("mappings.version-tag").as("version-tag")
    .push("mappings.address-aggregations").as("address-aggregations"),
  project("_id", "resource-id", "uri")
    .and("version-tag").as("mappings.version-tag")
    .and("address-aggregations").as("mappings.address-aggregations"),
  group("_id")
    .first("resource-id").as("resource-id")
    .first("uri").as("uri")
    .push("mappings").as("mappings")
);


AggregationResults<NetworkMapEntity> aggregationResults = mongoTemplate.aggregate(aggregation, "NetworkMaps", NetworkMapEntity.class);

测试一下，抛出如下异常：java.lang.IllegalArgumentException: Invalid reference 'mappings'!

四处搜索我发现有类似问题的人说这是 springframework.data 依赖项的错误，但在旧版本上，所以我认为我对 Aggregation 对象的构造可能是问题所在。我在解决方案的 Java 代码部分做错了吗？

Answer 1

虽然我仍然不明白为什么当前的解决方案不起作用并且想了解为什么不起作用，但我将查询更改如下，现在它似乎可以按预期工作：

Aggregation aggregation = newAggregation(
  match(Criteria.where("resource-id").is(resourceId)),
  unwind("mappings"),
  match(Criteria.where("mappings.version-tag").is(versionTag)),
  unwind("mappings.address-aggregations"),
  match(Criteria.where("mappings.address-aggregations.pid").in(pids)),
  group("_id", "resource-id", "uri")
    .first("mappings.version-tag").as("version-tag")
    .push("mappings.address-aggregations").as("address-aggregations")
  group("_id._id")
    .first("_id.resource-id").as("resource-id")
    .push(
       new BasicDBObject("version-tag", "$version-tag")
             .append("address-aggregations", "$address-aggregations")).as("mappings")
);