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mongodb - Mongo 聚合和过滤器

问题描述

我正在尝试使用以下查询过滤文档：

db.projects.aggregate([
    {
        $project: { 
            deployments: { 
                $filter: { 
                    input: "$releases.deployments", 
                    as: "deployment", 
                    cond: { $eq: ["$$deployment.environment", "Live"] }
                }
            }
        }
    }
])

的输出deployments始终是一个空数组，尽管如果我将条件更改为$nethen 它会返回所有结果。

如何获得过滤条件以仅返回deployment.environment等于字符串的记录Live？

这是一段 json 示例：

{
      "project_id": "1",
      "project_group": "A",
      "releases": [
        {
          "version": "1",
          "deployments": [
            {
              "environment": "Integration",
              "created": "2019-10-01T06:40:01.000Z",
              "state": "Success",
              "name": "Deploy to Integration"
            },
            {
              "environment": "Test",
              "created": "2019-10-01T08:23:58.000Z",
              "state": "Success",
              "name": "Deploy to Test"
            },
            {
              "environment": "Live",
              "created": "2019-10-01T09:02:17.000Z",
              "state": "Success",
              "name": "Deploy to Live"
            }
          ]
        }
      ]
    }

标签： mongodbaggregation

解决方案

releases如果您的查询是嵌入式文档，但它是一组嵌入式文档，您的查询将完美运行。

以下查询将遍历每个元素releases并过滤环境为 的部署Live。

db.collection.aggregate([
    {
        $project:{
            "releases":{
                $map:{
                    "input":"$releases",
                    "as":"release",
                    "in":{
                        $mergeObjects:[
                            "$$release",
                            {
                                "deployments":{
                                    $filter:{
                                        "input":"$$release.deployments",
                                        "as":"deployment",
                                        "cond":{
                                            $eq:["$$deployment.environment","Live"]
                                        }
                                    }
                                }
                            }
                        ]
                    }
                }
            }
        }
    },
    {
        $project:{
            "releases":{
                $filter:{
                    "input":"$releases",
                    "as":"release",
                    "cond":{
                        $ne:["$$release.deployments.0",null]
                    }
                }
            }
        }
    }
]).pretty()

输出：

{
    "_id" : ObjectId("5d93401ef2e6411a68a145ee"),
    "releases" : [
        {
            "version" : "1",
            "deployments" : [
                {
                    "environment" : "Live",
                    "created" : "2019-10-01T09:02:17.000Z",
                    "state" : "Success",
                    "name" : "Deploy to Live"
                }
            ]
        }
    ]
}

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