mongodb - Mongo聚合根据字段名收集数组元素

Question

我有一个聚合的 mongo 文档，如下所示。有两个不同的批次(“-Minor”和“-Major”)，每个批次也有“batchElements”。

{
    "_id" : "123",
    "info" : {
        "batch" : "Batch1-Minor"
    },
    "batchElements" : {
        "elements" : [ 
             { },  { }, .... { }
        ]
    }
},
{
    "_id" : "123",
    "info" : {
        "batch" : "Batch2-Minor"
    },
    "batchElements" : {
        "elements" : [ 
             { },  { }, .... { }
        ]
    }
},
{
    "_id" : "123",
    "info" : {
        "batch" : "Batch3-Major"
    },
    "batchElements" : {
        "elements" : [ 
             { },  { }, .... { }
        ]
    }
},
{
    "_id" : "123",
    "info" : {
        "batch" : "Batch4-Major"
    },
    "batchElements" : {
        "elements" : [ 
             { },  { }, .... { }
        ]
    }
}

如何收集“-Minor”和“-Major”的所有“batchElements”并创建如下文档；

输出:

  {
    "_id" : "123",
    "minorElements" : [
        [{}, {}, {}, ..... {} ], // elements of "Batch1-Minor"
        [{}, {}, {}, ..... {} ], // elements of "Batch2-Minor"
        ...                      // elements of "BatchN-Minor"
    ],
    "majorElements" : [
        [{}, {}, {}, ..... {} ], // elements of "Batch3-Major"
        [{}, {}, {}, ..... {} ], // elements of "Batch4-Major"
        ...                      // elements of "BatchN-Major"
    ]
}

Answer 1

您可以从 $split 开始获取批次的“类型”作为 $group 的一部分_id .然后你可以运行另一个 $group制作 minor和 major同一文档的部分。在最后一步你需要 $replaceRoot连同 $arrayToObject将两个数组提升到根级别。

db.collection.aggregate([
    {
        $group: {
            _id: {
                id: "$_id",
                type: { $arrayElemAt: [ { $split: [ { $toLower: "$info.batch" }, "-" ] }, 1 ] }
            },
            docs: { $push: "$batchElements.elements" }
        }
    },
    {
        $group: {
            _id: "$_id.id",
            data: { $push: { k: { $concat: ["$_id.type","Elements"] }, v: "$docs" } }
        }
    },
    {
        $replaceRoot: {
            newRoot: {
                $mergeObjects: [ { _id: "$_id" }, { $arrayToObject: "$data" } ]
            }
        }
    }
])

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